Actually it wasn't the first. Paul H. Tutmarc beat Fender by about 15 years with his Audiovox #736.
Fender was the first commercially successful electric bass, but even it got off to a slow start.
I don't think the music world was quite ready for it when Tutmarc introduced his electric bass ca 1935 and he didn't have the facilities for larger scale manufacturing and distribution. So lack of any real demand coupled with little supply resulted in oblivion for the Audiovox #736 until recently.
here's a link. hopefully you can read german! if not just look at the pictures
wish i could play one of these just to check it out!
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. They'd likely be surprised at how many B strings can be "fixed" without changing a thing on the bass.