Lots of strikes.

How do we know that that's not what the execs at these companies want?

If a union's governance is meek and not as sophisticated as other political systems, then it would make sense that the execs of companies would have no choice but to infiltrate such vulnerable systems in order to minimize the damage that they do.

These strikes cost the company money. If the companies have full control of the union's through such infiltration, then what do they gain out of "allowing" this to happen?