His current title is CEO of Google DeepMind. Becoming Chief Scientist of Alphabet seems to be a step away from the path to replacing Sundar, no?
P.S. I think his real interest is Isomorphic, and his new role will offer fewer distractions.
Perhaps now there could be a shift back to investing in R&D to get fresh monopolies.
He was the guy branding Google an AI-first company back when they invented the transformer.