@Olivier5,
When Sander first started to run for the presidency back in 2015 he did so by inferring the established democrats, long time democrats, are beholden to special interest groups. Right away he brought a divide in the democrat effort to place a Democrat in the WH over a Republican which benefited Republicans. While mentioning the problems and some of his solutions, some of which were agreeable, some not every democrat liked, he always had to get in something about "establishment Democrats." When his supporters started to flock to his rallies, they came away with that attitude of basically bad democrats vs. pure democrats.
Thus the long division started and only gotten worse as time went on. The election of 2018 should have alerted some of those purist folks that not all Democrats were on board with the whole Bernie thing as the candidates who did the best were so-called moderates. Although Bernie shares some of the blame for the divisive tactics of his Bernie bros and purist test, the whole movement in the way they carried out the movement is what was divisive.
Like others have said, Bernie deserves a lot of credit for forcing democrats in congress to remember who we are and fight to go more to the left than we had been in previous years.
Edit: by the way, there is more than one way to skin a cat. Just because we don't agree with Bernie's plans which are way too much put all together doesn't mean we don't care about health care and it is a cheap shot on your part to infer otherwise.