PART 1 OF 2

I know Sanders and his book - it's about Bartholomew Roberts. It's an "eh, okay" book since he doesn't leave any notes as to sources on things in his text. I find the earlier editions of Black Barty: The Real Pirate of the Caribbean called That Great Pirate: Bartholomew Roberts and his crew, 1718-1723 by Aubrey Burl as a better biography for Roberts (since it had endnotes to follow).

But onto your question, which is a good one - The TL;DR answer is: Unemployment of sailors after the War of Spanish Succession (1702-1713) had it's influence but wasn't necessarily the cause of it. The wrecking of the Spanish Treasure Fleet in 1715 was a sort of catalyst to a peak in pirate activity from 1716 to 1725, having areas with high value targets but little authority to reign in piracy allowed for piracy to succeed for a long time, and then the hard up employment issue exasperated it all. I wouldn't call the several thousand men who engaged in piracy at the time (around 5,000 men in total according to an estimate by Marcus Rediker in his work on piracy Villains of All Nations for the 1716-1725 period) a "large fleet" since they didn't all work together at the same time (it's a lot of pirates, but fleet suggests one that works together like a Navy fleet to me). As to why there aren't rashes of piracy after other wars afterwards, it depends on time and place since other parts of the world had notable periods of piracy afterwards.

For more, see PART 2 in my reply to this for the full explanation: BACKUP LINK (There wasn't enough room for my response with my TL;DR, so I had to go to a second comment)