This might be true about the board, I don't follow them enough to have a sense of that but it could also mean it's like most clubs - the coach doesn't get to necessarily dictate everything and most times, not sure that is a bad philosophy to have. City & Pep is an exceptional sort of case, there are few that are comparable and that's also a big reason why Guardiola is there, IMHO
I've also read their board intends to hire a DOF to assess the sporting side of affairs and that's probably warranted, if not long overdue. Still, even with a DOF you have to have agreement with your coach and Mou burns bridges everywhere.
I'd blame the board or one thing, the hire in the first place because there cannot be any surprises (Even the ones we've seen in 3 years) going into that agreement - Mou does as Mou is. Of course, they are American owners and are unlikely to prioritize the sporting aspects over the bottom line - irrespective of them being closely linked. Truth is United haven't been relevant for 5 seasons already but they continue to grow as a company - this is what the Glazers covet most, Mou might've just been a stopgap to appease fans and weather the Jose storm once he was most certainly let go