Medicare of All -- great groundswell, everybody's first choice, fire proof

Will somebody please explain to me what is so difficult about passing the health care plan that everybody (except the industry) loves the best: Medicare for All?

In my lifetime I watched LBJ ram through Medicare, Medicaid, a $10/hr minimum wage, etc., and yes, he could very likely have passed the Civil Rights legislation all on his own. Okay, that was on his own blackmail, bribery, cajolery or even reasoning together; LBJ the near tyrant -- but LBJ was working in a complacent period where he had to do it all on his own, unlike FDR who had vast public support for change.

There IS vast public support for universal health in this (Obama?) era and the broad preference is Medicare for All -- which Medicare happens to have much built-in flame proofing against the usual Republican flaming because it is already in place for our most vulnerable (the old who love it) and everyone understands exactly what it is.

Lets go over that: great groundswell, everybody's first choice and fire proof. Sounds like the path of least resistance to me -- but I've only been following American politics intensively since 1961 (age 17).