This is true, but I don't think VCs use young founders to prove an idea. A startup is a very different environment than an enterprise.. and it's very rare that a person can execute well at all stages. So eventually the startup grows to a point where more professional leadership is helpful.. and VCs will happily replace a founder if they think it'll make them more money.

There's a lot of research on this (and dating back quite a while.. not new at all). So here are just some quick links I found:

https://www.kauffman.org/-/media/kauffman_org/research-repor...

https://academic.oup.com/rfs/article-abstract/31/4/1532/4604...

https://hbswk.hbs.edu/item/the-founding-ceos-dilemma-stay-or...

https://www.businessinsider.com/how-often-do-founding-ceos-g...

Also this is a nice article about this from the Founders Dilemma (which is a good book also): https://hbr.org/2008/02/the-founders-dilemma