The Wachowskis weren't forced to, they, as humans, have the power to say "nu-uh". But I suppose they were made an offer they couldn't refuse.
Or worse: WB owned the franchise and were going to make a sequel with or without them (or the actors). I'm sure the franchise will get a "hard" reboot at some point.
To me Matrix 4 was sort of an admission by The Wachowskis that while they could create at least one 'perfect' cyberpunk movie, they couldn't really figure out what cyberpunk should lead to - what a good subversion of the genre should look like. It feels like they tried but kind of gave up half way there. Subverting a franchise that people already have such strong and established connection to is probably almost impossible.
Or worse: WB owned the franchise and were going to make a sequel with or without them (or the actors). I'm sure the franchise will get a "hard" reboot at some point.