To be fair to them there are still a few projects which are still hosted on SF, in some cases it's the only place you can find specific legacy projects.

So if their calculation was that all of open source would stay on their platform with them adding malware, they were wrong. But if the calculation was that a long tail of random small and semi-orphaned projects would stay there after the big popular projects had all migrated, providing them with essentially free revenue for a very long time, they were kind of right.