That's literally every rich tech CEO though. All of the FAGMAN companies use hundreds of open source projects internally, and even when they do contribute back they end up driving those projects in directions that benefit their bottom line above all else. Presumably they wouldn't contribute at all if if the dollar cost of an internally-developed equivalent wasn't even higher than contributing to OSS.
I don't have any stake in this drama since I haven't used WordPress for something like 13 years, buy to me this feels like crab bucket mentality, going after Mullenweg because he feels like a target that could actually be taken down as opposed to people like Zuck/Page/Brin/Nadella/etc who are truly untouchable. The level of vitriol just seems unreasonably high for something that isn't really that big of a deal.
Maybe if he wasn't personally and very publicly trolling an entire open-source community, which has created financial burden for users, then people in that community wouldn't be so upset.
