Facebook, Amazon, and Microsoft were a product of very good timing, but I think we should not undersell how high the barrier to entry for Amazon and Microsoft were in the 90s and 70s specifically.

Amazon basically started at the dawn of the internet, and I actually remember using it in 1997 as a fifth grader. It was incredibly well developed for that very early time period compared to just about everything else.

Microsoft's first product was a BASIC interpreter written on a PDP mini-computer in assembly, and was written so quickly, Paul Allen wrote an entire emulator in assembly for the actual chip they were trying to run their software on. The bootloader for the tape loaded program had to be entered in binary onto the machine they were trying to run the software on. There were about a dozen people in position to create this sort of software in the world at the time and only two who could do it in a 6 week timeframe.

Bill Gates and a lot of these other billionaires are in totally different leagues when it comes to origin story.

You see a lot of people start a successful business, and then fail at their next venture. That doesn't mean they're incompetent. Everyone swings and misses sometimes.

But, if there is eventually a patten of failure, either luck was a factor, or perhaps the person themselves has changed.