There are even larger areas in cryptography where if you don't do it right the whole thing will work, and after a few months someone will make $1B by crashing your currency into oblivion.

Edit: if you want to see how that can happen, I like to take apart weak cryptocurrencies and show what's wrong with them. Someone paid me to do a public review of a thing called Stratis a while back, and I went to town. Here's a highlight. https://twitter.com/PLT_cheater/status/1235036182284820481

I still accept commissions doing code review. It's just too much fun.