[akvadrako]

Do you think that many quantum physicists during the 21st century accepted the possibility of living in a splitting multiverse?

I don't think that's historically accurate. If you read about how Everett's ideas were treated it's pretty clear traditional QM is antithetic to many worlds.

[ithkuil]

Sure, I agree with you that most people vehemently rejected that interpretation.

But the QM theory is not its interpretation.