As mentioned, the novelization describes Snoke's attack as your typical FL:
Kylo felt rage ignite deep inside of him--ignite and become an inferno demanding release.
But Snoke had anticipated that, too. Kylo had only taken the slightest step toward his master when lightning erupted from Snoke's fingers, blasting Kylo backward and leaving him reeling in pain.-TLJ
So I think that was just how Rian Johnson chose to depict the ability.... cuz realism, lol.
That said, the comic book adaption of TLJ also depicts Snoke's FL as it is shown in the film:
https://i.imgur.com/5d0KtiV.jpg
...But that's to be expected. /shrug
It was being sprayed everywhere and hit all things which were conductors of electricity. The small burst of lightning which Snoke unleashed became attracted to the ONE conductor that strong enough to attract the lightning. Palpatine's lightning was large enough to create have all conductors of electricity in a sphere around it attract some lightning. That caused everything around Sidious (including himself) to get electrocuted.