I'm surprised they only have 500 employees to be honest, but there's a good chance a lot of the work in the space is done in collaboration with other companies and open source contributors
They are going big on scaling Ethereum with zero-knowledge (or more accurately, succinct but not necessarily zero-knowledge) proofs. I used to work for one of their competitors also in that project, but all the Polygon people I've talked to on the ZK side are very sharp.
As an adult you have to stop playing what if all the time with your past or you'll get paralyzed about every decision you're making now. Or sink into a depression that shortens your life expectancy. But thoughts about perfect trade execution aren't just childish, they're pure fiction.
If you did things over you still wouldn't be a billionaire. Stop picking at that scab and go do something life affirming.