I used to believe that absent the lawsuits that BSD would have been THE choice instead of Linux, but I think there's a lot of truth to the position that Linux was far more experimental and evolving rapidly -- and exciting! -- than FreeBSD (et all) which were busy doing things like powering the biggest web companies of the 90s (Yahoo and many more). Making waves and iterating rapidly was never going to mesh with the Unix Way (even open source Unix). As such, Linux got the mind-share of hackers, idealists, students, and startups and the rest is history.
(I think it's a pity that the useful innovations that happened in Linux cannot be moved back over to FreeBSD because of licensing -- the computing world would be better off if it could.)
Serious question, what innovations in Linux would FreeBSD even want? I honestly can't think of any.
IMO it's Linux that should want the features from FreeBSD/Solaris. I want ZFS, dtrace, SMF, and jails/zones. Linux is basically at feature parity, but the equivalents have a ton of fragmentation, weird pitfalls, and are overall half baked in comparison.
For example, eBPF is a pretty cool technology. It can do amazing things, but it requires 3rd party tooling and a lot of expertise to be useful. It's not something you can just use on any random box like dtrace to debug a production issue.
(I think it's a pity that the useful innovations that happened in Linux cannot be moved back over to FreeBSD because of licensing -- the computing world would be better off if it could.)