Also important:

This tech has been around for about 25 years already, first success was 1998...

Johnny received his implants in March 1998. During a 12-hour operation, Bakay inserted the electrodes, housed in two glass cones, into the area of Johnny's cortex that controls left-hand movement. Once the cones were implanted, the doctors believed that axons -- parts of the brain cell that transmit electrical impulses -- would grow through them. When an impulse passed along an axon, it would be intercepted by tiny gold contacts and transmitted through the electrodes. ''Axons are really like telephone lines,'' Kennedy explains. ''We're just diverting the lines and eavesdropping on the call.''

The hope was that by imagining he was moving his paralyzed left hand, Johnny would cause an increase in electrical impulses passing among the neurons there. These impulses could then be transmitted by the implanted electrodes to a receiver placed on Johnny's pillow, and from there, the analog brain signals could be translated into digital commands that Johnny's computer could understand. In theory, by controlling the frequency with which the neurons in his motor cortex fire, Johnny could move a cursor up or down, left or right on his screen.

https://www.nytimes.com/2000/06/11/magazine/tech-2010-07-brainpower-making-contact-the-mind-that-moves-objects.html

Musk is just paying people to miniaturize existing tech and is using marketing to make people believe he's personally inventing it

The bad part is his absolute disregard for basic lab safety and pretty much any other regulation.

It's like how SpaceX doesn't care how many rockets explode, Musk probably views early adaptors as sacrificial lambs.