Hmm ... you don't have to ask for consent. You just slap the license you want to your code and that's it.

It's not some sort of democracy, lol, it's a set of exclusive rights that are created the moment the work being copyrighted is produced.

(For a quick intro I recommend: https://www.youtube.com/watch?v=bxVs7FCgOig)

In the case of the license in question (L/GPL), it's one of the most strict ones out there, it explicitly forbids relicensing code under a different non-compatible license, like MIT; let me says that again, L/GPL EXPLICITLY FORBIDS the thing that happened here from happening.

I sympathize with the guy that spent 12 years of his life maintaining the code, thank you for your service or something, but that does not make a difference. The wording of the (L/GPL) license is clear and the original author and most of the other 50 or so contributors did not approve of this.