If he's regretful, treated and paid his time? Yeah I think so. It didn't show particular signs of cruelties and he was legit insane at the time. Harboring grudges, even if justified, for decades and making it your lifelong mission to keep following and resenting and attacking a person means your life will also be stuck in that day.

Doesn't mean I'm going to personally embrace him and invite him in my house like some people do.

Languages study in general. People never stop to think about language families.

For example, why it took millennia for people to realize how closely related were Greek, Celt, Latin, Sanskrit, Scythian, Persian and German (all are Indo-European) despite more or less intense exchange between people using them?

Because we didn't have grammar rules or standards, so patterns were insanely hard to distinguish and could vary from location or speaker.

So instead they had a feeling that things were similar, which ended up with a lot of them assuming things an universal kind of base for everything.