Things are a lot different these days to when SAF took over as manager. Revenue, advertising and CL qualification, I think, mean a lot more since the EPL started in1992.
Even if Moyes has the backing of the Glaziers, it's important to have the backing of the fans, sponsors and TV broadcasters (who are responsible for the bulk of their revenue).
Money talks in today's game and if fans don't buy shirts and broadcasters don't pay CL television rights, their hand may be forced. We shouldn't under-estimate 'fan' power. Look what happen to Benitez and Man Utd's global fan base is huge.
Aside from the poor performances, there's rumor on the grapevine that certain players are not happy with Moyes training regime, especially RvP, who has claimed it has made him more prone to injury.
Interesting times ahead at Old Trafford.