Snoke was only a big mystery because fans proposed endless theories - there’s nothing in the film itself that invites such rampant speculation.
What about a horribly disfigured and extremely powerful force user that’s the leader of a mysterious new group that took the place of the dead Empire and somehow influenced Ben Solo to turn to the dark side (which everyone in TFA and TLJ kinda acknowledges but there’s still no explanation as to how that happened) and murder his father, fellow students, and attempt to murder his uncle DOESN’T invite speculation?
Sorry, “invite” was the wrong word, I think “demand” or “require” was closer to what I meant.
Well, that’s up to each of us to decide. You may feel it doesn’t require an explanation, which is perfectly fine, but others like myself may feel differently.