I don't recall them refusing to support x86, but BSD development was mostly done by academics rewriting and improving AT&T UNIX, which was mostly on big iron systems of the time. They were focused on academic computer science work. The lawsuits stopped a lot of BSD work as the universities were sorting it all out. William and Lynne Jolitz start porting 4.3BSD to the Intel 80386 at Berkeley in 1989 (but the code wasn't released for years due to said lawsuit) before Linux existed. That is the first BSD-on-x86 work; by December 1990 they had contributed a working port to UCB. Most of the code didn't see the light of day until ~1992.

Also, usable and production ready BSDs were running large websites on x86 long before linux became mainstream and well-supported enough to be used. The BSD TCP/IP stack was the reference implementation for ages and BSD was heavily used in the internet's early days as a lot of early companies spun out of Californian universities. Hotmail ran on FreeBSD. Early SunOS variants were based off of BSD, as were some other commercial unixes.

The bigger killer, I think, is that BSD was (and still has) a bit of closed mindset to newcomers and were and are more conservative to new technology, despite some foundations of techbeing started with them. Docker's origins can be directly traced to FreeBSD jails. Sometimes the conservatism is warranted and a benefit (eg OpenSSH).