Mandatory national insurance was the sweetener to get the congress critters who were in the pockets of the health insurance lobbyists to vote for the bill.
Mandatory insurance is the only way you can set up a system with mandated coverage for preexisting conditions. Otherwise, why would anyone get insurance? You could always wait to buy insurance until you developed an expensive problem.
The home owners insurance companies would soon be bankrupt if the government mandated coverage for preexisting fires.