Just having books doesn't make someone a genius if they don't know how to act upon the things written in the books.
Vegapunk is still a genius.
The 500 years ahead of the rest of the world hype comes from other people anyway. The guy didn't hype himself like that.
Saul being alive is trash tho.
Nothing is gained by having him back. Yes, I know the island was burning and he was frozen - it would've been easy for him to thaw out. But he had a great send off which is tied directly to the only characterization Robin ever had.
Which is why I think this is another case of leakers fucking with us.