It's true that large firms and NPEs hold the patents and can better enforce their patents, but "patent trolls" (aka patent license companies that specialize in holding and enforcing patent rights as a business model) can be in some ways a benefit to smaller firms for a couple of reasons:
1) The smaller firms don't have the ability to aggressively defend their patents against larger competitors (and would simply have their invention used by the big players without a patent). Instead, the smaller firm can essentially outsource this to a patent licensing firm that specializes in it (standard division of labor), for example selling the patent while maintaining a license to use it themselves (or any other of a multitude of arrangements that essentially let them fight the big players).
2) If the smaller firm doesn't have the resources to actually introduce and sell their invention in the marketplace, they can sell it to a patent licensing firm that can use the patent within their portfolio to license to the main players in the market. This could arise when, for example, the small company comes up with an important new innovation in smartphones, but the small company lacks the resources to actually create a viable physical product on its own.
1) The smaller firms don't have the ability to aggressively defend their patents against larger competitors (and would simply have their invention used by the big players without a patent). Instead, the smaller firm can essentially outsource this to a patent licensing firm that specializes in it (standard division of labor), for example selling the patent while maintaining a license to use it themselves (or any other of a multitude of arrangements that essentially let them fight the big players).
2) If the smaller firm doesn't have the resources to actually introduce and sell their invention in the marketplace, they can sell it to a patent licensing firm that can use the patent within their portfolio to license to the main players in the market. This could arise when, for example, the small company comes up with an important new innovation in smartphones, but the small company lacks the resources to actually create a viable physical product on its own.