Neuralink was initially designed with the intent of basically making people into semi-robots, capable of interacting with devices and communication systems and things like that. The new claim that its purpose is for medical use is kind of, in my opinion, just Elon's way of jumping on the medical bandwagon. He's an idea guy, and this idea may be further developed by neuroscientists, but he doesn't actually know anything about the biological mechanisms behind it. There are many other scientists working on technology like this, ie Neuropace, bio-feedback walking assists, etc. He's better off funding it than actually trying to deduce its potential. Bill Gates funding HIV research doesn't make him a doctor or epidemiologist. And even with an implant in your skull, you're still susceptible to the millions of other health ailments it doesn't aim to treat.