Given that the DC Extended Universe has been one misfire after another save for Wonder Woman.
He has made $46 million in 2016. There's "I'll do anything for money" and then there's "Really, Zack? I could buy a Papa John's, y'know."We know the main reason Affleck signed up was the solo Batman movie. He thought he had a cool idea for that, and he and his team banged out a script. Then it went to review and rewrites. He said he'd still direct if he liked the script that emerged from that process. Obviously he didn't, because they brought in someone else and started over.
He was also angry about his personal project "Live by night" that was essentially ignored by most people during interviews and things in favor of batman related questions because the role is such a large one. He underestimated the amount of criticism he would receive for poor movies like BVS. He has his own personal problems such as his marital status and his alcoholism that are affecting him also.
Now Reeves has said he has an idea for a trilogy. If Affleck's not in for the long haul (and they've given him no reason to stick around) then replacing him before they start makes sense. It seems that Affleck wants to find a way to exit the role without burning bridges.