I figured that Warren wasn't pulling as many votes away from Sanders as his supporters claimed.

Honestly, the Sanders surge wasn't particularly large.  It only felt that was because he was winning races, even if it was by only a point or so.  Here's the RCP average for the race.

January 1:  19.1%
February 3 (Iowa Caucus):  23.1%
February 29 (S. Carolina and peak of surge):  29.6%

So we're only talking about 10 points or so and never above 30%.  That much could be attributed to a bandwagon effect after Biden collapsed and suddenly Sanders was leading and then the subsequent bounces from his wins.

If you look, Warren stayed pretty steady during the early part of the Sanders surge.  She was at 15% on January 1 and stayed right there until around New Hampshire (and still only leaked a couple of points).  He might have lost a few voters to her at her peak, but it looks like they'd come back to the fold by the end of October.

Warren might have nabbed a few Sanders voters at her peak, but looking at the chart, it seams that they'd gone home by the end of October.

Soo, a bit surprisingly for me, the whole Coronavirus crisis plays into the debate about health care. How so?

Well, many people still working with small symptoms, because they don't get paid sick leave. If they work in a job, where they are in contact with other people, this helps to potentially spread the virus (or basically any infection).

Also people without health care may avoid going to the doctor, in which case they aren't identified as infected with Covid in time.

All this is not helping to contain the epidemic.

That's less policy than bad luck.  Most of the deaths (and a good chunk of the total known cases) in the United States so far have come from an outbreak in a single nursing home.  The United States was unfortunate in that one of the first detectable outbreaks happened in pretty much the most vulnerable place imaginable.