1. Rey and Kylo Ren’s connection means Snoke is still alive
We’ll start with a soft ball. Snoke revealed in The Last Jedi that he was behind the psychic connection between Rey and Kylo Ren, which he manipulated to draw our young heroine into a trap. We see that the connection persists up to the end of the film (after Snoke’s apparent death), so Snoke must still be alive.
After space flights and Force projections across the galaxy, we’re not entirely comfortable in putting limits on how the Force works (although here’s a hint: it’s however the writers want it to). So it’s hardly an ironclad argument.
2. Snoke was a puppet
AKA ‘The Amidala Bait-and-Switch’. Snoke was some kind of smokescreen (a ‘Snokescreen’, we guess), with someone else pulling the strings – maybe almost literally according to theories that the being we saw was a cadaver being manipulated by the Force. Perhaps that’s why his bisected remains were so hilariously floppy.
As to the puppet master, this has proved a boon to fans who can’t let go of the ‘Snoke is Darth Plagueis’ theory. We can see the reveal now: “It’s me! That guy who was mentioned briefly in Revenge of the Sith. Surely you remember..?”
3. Snoke was a Force projection
Anything Luke can do, Snoke can do better. If Luke can create a mostly convincing projection of himself from across the galaxy, then his evil nemesis can make one that interacts with the objects and lightsabers flying all around, and can even pretend to have been chopped in half.