They also benefit from the stability of operating within a pretty known system and the fact that they are able to afford legal expertise. Big businesses may get hurt by patent trolls, but I’d imagine that this is less strategically important to their business than using their patents to prevent competitors from starting up or from taking away their business.

Small businesses get hurt the most by the patent system. A patent troll can bankrupt them or make them unfundable, big business can squash them (perhaps offensively, eg a big business takes a small business to court even though they can’t win, so the small business can’t raise funding and has to pay tons in legal costs), and they still have to pay lawyers for advice on how to protect themselves even if nobody goes after them.