Any firm with a truly valuable product could buy the patent (or at minimum, a license). This is basically Coase Theorem 101. At this scale, transaction costs are not significant and so the property right will end up allocated to the most efficient holder.

Even if you don’t like that pure theory point, litigation is expensive and takes a long time. If some small little patent holder is really being stubborn and you’ve got something valuable, it’s not that hard to grind them into dust while you get big. Litigation financing makes this a little harder than it used to be but still.