“....Not to drive a business into the ground....”
The problem is union leadership never suffers when that happens. The rank & file are on they dole, the leadership just moves on and organizes someone else.
Your answer of the rank and file never suffers and just moves on is spot on. That is the ‘career model’ taught in business classes in colleges for a couple decades now at least.
I remember instructors teaching how just to enrich yourself and move to another job. Your job is just to make as much money as you can and move on. Because ‘everybody’ has many jobs during their career and it isn’t sensible or possible to stay at any one company. Not a one of them cared about the success of the business.