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Why did piracy thrive in the late 17th and early 18th centuries?
Was it because the sailors in the Royal Navy and privateers were not satisfied with their pay? Was it because since many wars were ending there was just less demand for seamen?

I've researched a few websites and none of them give a concrete answer as to why it began.

If an answer could also include certain wars and other resources which would be good for understanding the golden age of piracy from its origins, that would be great.

The creation and expansion of European empires during the Age of Discovery resulted in the expansion of trade routes to new colonies and trading posts across the world. The vast areas of these trade routes were far larger than the new empires' navies could effectively police, which meant that merchant vessels moving along them were essentially responsible for their own protection. It also meant that pirates could establish bases that were, effectively, out of reach of the colonial powers. Expansion of the European world also resulted in greater "interaction" at sea with other world powers, much of which would be classed as piracy by the Europeans.

As a merchant ship owner of the time, you had to balance defending your vessel against making a profit from the voyage, e.g. the more guns you had, the larger the crew you required and both of those meant you could carry less cargo. Ships of the period were comparatively small and the cargo space wasn't all that large to begin with. This generally meant that trading vessels were far more lightly crewed and armed than any pirate vessel that preyed upon them.

Competition between the European powers during this period led to conflicts of interest which, in turn, often lead to full-scale wars. These were fought out across the oceans as well as on land. During the 17th Century European states were just starting to raise standing navies. Because of the cost, these were kept small and usually had to increase significantly in size at times of war. The number of available armed vessels were swelled by issuing letters of marque to merchant ships to act as privateers. In wartime, governments often overlooked the past activities of seamen and awarded letters of marque to men who were previously pirates (greatly blurring the distinction between pirate and privateer).

During times of peace it wasn't economical to maintain large fleets so most of the ships' crews were disbanded. The merchant and fishing fleets could only absorb a certain number of the released seamen, so the remainder had to find other employment. The alternative jobs on land were unskilled and, consequently, low paid making life as a pirate seem comparatively attractive. Thanks to their wartime activities, these men would have all the skills that they would need as pirates in hunting down and capturing ships. As a ship master (who was often the owner), if you had operated as a successful privateer during a war it may have been very tempting to cross the line and operate as a pirate once the war ended.

Additional reading:
Life Among the Pirates: The Romance and the Reality, D. Cordingly (1995)
The Sea Rover's Practice, B. Little (2005)
Piracy: The complete history, A. Konstam (2008)
Pirates of Barbary, Corsairs, conquest and captivity in the 17th Century Mediterranean, A.Tinniswood (2010)

Prior to the invention of an accurate chronometer, a ship wishing to visit an isolated island would need to either sail to the correct latitude from a position known to be to the east of the island and then head west, or sail to that latitude from a position west of the island and head east. If a ship that tried to visit the island from the north or south were to reach the correct latitude without encountering the island, the captain would have no way of knowing whether the island was to the east or west. If the captain thought that the island was within 50 miles east or west (but didn't know which) the captain might try sailing 75 miles east and then, if the island still isn't found, try sailing sail 150 miles west, but unless a captain got lucky it would often be necessary to abandon one's target and switch to trying to find some other island which was known to be east or west. Since getting lost could double the amount of time a ship might have to go without restocking, it was something to be avoided at almost all costs.

A consequence of this is that the a pirate who sailed a moderate distance east from an island would know that any visitors arriving from points east would need to sail quite close to him, and a visitor who tried to sail north or south to avoid the pirates before heating west past them might sail past their destination.

Dava Sobel (1995) Longitude ( borrowable at archive.org )

I think the most basic reason is that trade ship and military ship were basically the same thing. That meant that every trade ship was basically a potential pirate ship that was reasonably close in capability to both it’s target and any defenders.

Piracy mainly went out of fashion when a single warship could utterly destroy any trade vessel. Which meant that you were either built for war or for trade. If you were built for war, well either you were associated with a nation that could be held responsible for your actions or you were clearly a danger that needed to be eliminated.

Quoting Wikipedia on the galleon:

The galleon continued to be used into the 18th century, by which time purpose-built vessels such as the fluyt, the brig and the full rigged ship, both as a trading vessel and ship of the line, rendered it obsolete for trade and warfare respectively.

And then there is the Santísima Trinidad which had 60 guns and could carry 5,000 crates of cargo.

There's always been piracy, everywhere from Ancient through Mediaeval time to the Renaissance; but after that event Europeans now had sail-bourne [ and not galleys ] ocean-going vessels --- which just like non-pirate ships, no longer had to hug coasts as much as was safe.

Apart from the fact vacationing in the Caribbean was now possible, it meant pirates could sail away quickly from trouble [ until the English Royal Navy caught up with them for good ] and dock in small islets, as well as Porte Royale, after making a deal with the natives about as nice as most, more official, deals were.

Pirates down in traditional pirate seas were from all European countries, much more than the usual Bristolian-speaking Britons of yore, such as Long John Silver or Captain Sharkey, or real pirates such as Calico Jack or Blackbeard Teach: they were in every sense of the words a very mixed bunch, and very democratic.