Amazon partnered with Berkshire Hathaway and JP Morgan on that project. They had a built-in base of employees larger than the population of Wyoming. Still failed.
There is plenty of space for VC backed start-ups to compete in healthcare. It would be foolish to go head-to-head with a company like HCA or UnitedHealth Group. But there is a lot of opportunity to sell them better software which improves the experience for everyone in the system. Or build better medical devices or improve efficiency in the drug development process or a zillion other niche areas.
Y Combinator has already funded several Epic competitors in the EHR space including DrChrono, Medplum, and Akute Health. Always room for more. The requirements for an EHR that can work in any provider organization are so overwhelming that no startup could directly compete against Epic. But a startup could initially target a particular medical specialty or facility type that Epic doesn't support very well, then expand out from there.
Patient and health care regulation, for good reasons, but basically the number of shoulders to spread individual risks across (aka insurance). The latter is much easier when backed, directly or indirectly, by nation state households and budgets. Nothing beats the ability of controlling your own currency.
Especially not VC backed start-ups...