I think views on healthcare would change rapidly if employers were prohibited from providing it as a benefit and all people had to get it privately. Even if employers raised salaries in accordance the shock people would have seeing the full cost of insurance would stir discontent.
The answer as others have pointed out is obvious. Medicare for All is something every business owner should support to simplify their own lives. (Ignoring that it’s just good business decision for “USA, Inc.” since it’ll save the country money.)