Neuralink has a technology that specifically addresses two of the main issues with BCI: data density, and implant effective duration.
There are more issues, but it addresses those two in particular, which is something quite interesting to see, and can be turned into patents that can be sold to other BCI initiatives.
The rest of Musk is… well, he’s kind of an “unstable genius”, with enough money to blow on random moonshots, marketing stunts, and random publicity. Honestly, if I had his money, I’d probably do the same: build a few core businesses, then go on tangents to see what sticks to the wall. It can all still be seen under the general theme of “colonizing Mars” though, which is a guiding starshot as good as any, with Hyperloop and Boring company having kind of exhausted what can be done on Earth, Tesla being a borderline failure, SpaceX, StarLink, or indoor farming working pretty well, and X being an experiment at social manipulation.