Yes, some could have invested for that reason. I do not think the largest stakeholders would have though, they have seen it as a risk.

The fork changed the rules in the middle of the game.

Every fork does this.

What is to stop witnesses from removing stake they think might have been stolen?

Nothing. Never has been anything to stop this. The functions they used have always been available to them.

The witch hunt mentality of the spam fighting groups doesn't inspire confidence.

I have been here for long enough to know that the amount of SPAM and plagiarism on the platform sucks. I do not think that many people enjoy downvoting - but no one enjoys picking up trash on the highway either, yet people still through garbage out their car windows.