Actually, rather than ask what caused the Vita to flop, we should ask why the 3DS was relatively so successful. It had many of the same issues to begin with: high price, poor marketing, features that people didn't like, competition from smartphones, etc.
Meanwhile the 3DS has gone on to do pretty well.
I personally think that the 3DS has Pokemon to thank, to be honest. It was directly responsible for millions of sales over the years, and those millions of sales encouraged other publishers to jump on board with the system.







