Almost no one reads all the fine print in their insurance policies (hence the acronym TLDR.)
But as others have pointed out, at best health insurance generally covers only “reasonable and customary” charges for medical care. Those are for accepted therapies and procedures; they generally don’t cover anything considered experimental (clinical trials, for example.)
Most health insurance policies do NOT cover things like custodial care - help with bathing, dressing, using the bathroom and so on. This can be a huge ongoing expense and less than 10% of the population purchases long term care insurance, which is typically the coverage that pays for assistance with “activities of daily living.” (Medicaid does cover some of these costs if someone qualifies.)
Very few professional horsemen have disability insurance. The last stats I’ve seen suggest that maybe a third of employed people have long term disability coverage, and that is almost always through an employer.
I am not aware of any insurance product that covers costs such as modifying a home for a newly disabled person, obtaining modified vehicles, housing for families near treatment facilities, etc. Those are also significant expenses.
My heart goes out to this horseman and his family. SCIs are devastating injuries and for an active young person like Kevin, the impact is obviously enormous. His wife has written that he had a complete injury to his c-spine which is unfortunately a very challenging situation. That may be why they are considering the avenue of clinical trials. Keck Medical Center recently announced some very promising results from their new stem cell therapy, but I don’t know if that procedure would be of value to someone with a complete injury or not. (https://news.usc.edu/107047/experimental-stem-cell-therapy-helps-paralyzed-man-regains-use-of-arms-and-hands/)