Well, I think the difference between Snoke and Palpatine is that Palpatine didn’t exactly need a reason for existing. He was powerful with the dark side, he was the emperor of the galaxy, that was all we needed to know.
But Snoke, on the other hand, definitely needed a reason for existing. Palpatine was supposed to be the last Sith, and it was never even hinted that there might be other Sith more powerful than him. So when Snoke gets introduced, it just feels like the writers pulling a new threat out of their behinds. If you’re gonna undo the destruction of the Sith and have a guy even more powerful than Palpatine pop out of nowhere, you better have a good reason for it. I don’t want a long-winded technical explanation, just something that could cause this new enemy’s existence to make sense.