If I were Facebook and a patent troll, I would closely inspect what Preact does and what patents I have that cover it and then go out and sue every company open

If I were Facebook and a patent troll, I would closely inspect what Preact does and what patents I have that cover it and then go out and sue every company openly using Preact preemptively because switching from React to Preact indicates they might be planning to sue me in the future (and if I bankrupt them, I might acquire their patents this way). That Facebook isn't doing this should tell you something.