This is SO naive.
Look around the world at major businesses, businesses far, far bigger than Manchester United (which is actually majorly small time in the grand scheme of things).
You don't think these businesses make bad decisions due to customer pressure? That's all fans actually are - customers. Same as movie goers or people going to gigs etc.
Yes, businesses make terrible decisions in attempts to appease customers ALL the time.
Disney are a recent, very high profile example of this. They are miles bigger than Manchester United. You think that keeps them safe from caving to consumer pressure?
Money makes the world go round. Customers, fans, consumers are what bring money to the table. When they shout loud enough, many companies can (and do) react to it, even if it's clearly the wrong thing to do.
Do you think the club's handling of the Greenwood situation wasn't affected by fan sentiment at all? Maybe you agree with that though because it aligns with your view on it.... But then you're cherry picking when you're happy with companies listening to consumers and when you aren't......
The George Floyd situation was affected HUGELY by public sentiment. If the justice system of one of the most powerful nations in the country can be steered by public sentiment, do you really think a football club in England can't?
Why have fans been protesting if they think leadership is immune to their opinions? You can't on one hand buy into fans being the most important thing about a club and then on the other just assume the hierarchy won't be swayed by them.....
Fans voices do have an impact. A massive one. You can like it or not, it's irrelevant, it's how it is and will continue to be.