What’s unclear with Dooku are his motivations. He reveals Sidious’s plot to Kenobi, but then we learn he’s actually working for Sidious, so why did he reveal the plan? For the majority of AOTC we are lead to believe that he is seeking civil war against the Republic (for independence I guess? Unclear the Separatist motivations), and then we find out he’s enacting out Sidious’s orders. So we are I guess left to believe it’s just galaxy domination/Sith at last getting revenge? Which is fine, but it’s messy and muddled for him.
For Snoke, first of all he’s not the primary villain of either film he’s in, second, his plan is clear from the start - eliminate the Jedi and destroy the Republic.
It’s plain as day though. Dooku, partly like Anakin, was a political idealist who became evil. The seperatist cause is irrelevant because the whole war is a false flag, and Dooku tells Obi Wan SOME of the truth because he’s doing what all Sith do, trying to become the master.
As for Snoke, WHY does he want to do those things? Also he’s not the primary villian by screentime, but he IS the big bad and inciting actor of the problems of TFA and TLJ.