The 'left' on this site never seemed to like Dominic Cummings before. Suddenly he seems to be 'flavour of the month'.

That is not what I am seeing. Most of comments I have seen from those on the left are roughly the same as mine: Cummings is untrustworthy and has probably been extremely selective in what he chose not to say, as well as what he said. There are, however, lots of ways of checking various parts of his remarks: videos, Hansard entries, the experience of care homes and many others. So we do not rely on what Cummings said in isolation.

Conversely, I have yet to see an argument from the other side that is much more than "Cummings cannot be trusted." If there is a detailed account anywhere it support the government's statements.

For reference here is the relevant Hansard entry of the discussion on 19th May 2020.

I would pay particular attention to which statements are in the present tense (i.e. saying they were happening at the time) and which are in the future tense (saying they are planned but not happening). I would also suggest people think about phrases like "Fourthly, we are supporting care homes to get the PPE that they need." It does not, for example, mean the homes actually have the PPE they need or are getting it. You could claim a leaflet describing PPE was such support if you felt inclined.