Don't blame Fender for not needing a bass amp company. They've been making some of the best bass amps for over 50 years. What was the inspiration for the Alembic F2B? Fender, of course.
If they didn't need a bass amp company, why did they buy it? No one held a gun to their head.
And it's pretty arguable about whether their bass amps have been the best. While I love the sound of a vintage Showman with a JBL cabinet, the Sunn cabinets sound a lot better than the Fenders, for the 60s thing. But even that fell by the wayside in favor of Ampeg and and then Acoustic amps by the start of the 70s. No one I knew in the late 70s or 80s was playing Fender bass amps, except a few of the blues guys.
The preamp that Alembic copied was from the Fender Showman, but that was not an original design by Fender. Fender used tube manuals by Western Electric and RCA, which was pretty much standard behavior for amp manufacturers back in the day. Gibson was already using a very similar tone stack in their GA-77 in 1953. By the time Alembic started manufacturing the F2B, the circuit was a classic that was decades old, with a basis perhaps even back to the 20s.