Evans has wanted to get out of acting to direct for years now; he phased himself out to the point his MCU work has largely been the only projects he's taken lately and he apparently opted not to renew his contract, instead working on a per-film basis after it ran out. It's got nothing to do with [insert agenda here] unless/until we hear it from his own mouth.
As far as Hulk, the Hulk's movie rights are in a messy spot right now. Solo films headlined by the Hulk have to split profits with Universal, at least until Marvel can resecure full movie rights, and furthermore, Marvel seems unwilling to give the Hulk another outing on his own after The Incredible Hulk didn't meet expectations. Banner just seems to work better in the MCU as a deuteragonist/supporting role.