People forget it and move on to something else.
It's a football club, a group of supporters being negative towards the owners, state of things etc, isn't exactly something new... Sponsors aren't going to fork out massive compensation fees and cancel their contract as a result. The people protesting are hardly the number one customers at the mega store.
People are too naive, it would take an epic company PR disaster equivalent of someone being guilty of metoo while being racist for sponsors to flee from us.
The type of protests required, over time, to even get close to a point where it'll be proper annoying for the higher ups, i don't think it's possible.
After the yanks took over the club, fans weren't even able to stage a mass walk out of the stadium, boycotting and targeting sponsors had zero effect, yet this time around it's suddenly going to work wonders.
I reckon that forcing someone like these cnuts out of the club is going to be close to impossible, and that the priority should be to avoid burning bridges. Right now there's support to the cause because of the SL disaster, but that support won't last long. Major protests that delays matches etc is going to win the PL over, or any politicians.