Many pathogens dampen the immune system for a while after the initial infection.
Covid does seem particularly good at it, with published evidence showing that it can last for 6 months or more (obviously not everyone will get the same degree of dysregulation, or for the same duration, but it happens, and can be enduring - it's not linked to severity of initial infection, seen also following mild and moderate infections, though more common with severe)
We are seeing more cases of diseases that are pretty effectively prevented by wearing masks - that's why it's only some diseases that have particularly high numbers this winter virus season. The greater numbers are because we are (perhaps) seeing two years worth of susceptible cohort rather than one.
But also remember that DC were back in school over 18 months ago, and some parts of the population were never in lockdown. Also that this phenomenon did not occur when it might reasonable have been expected - the first winter virus season after ending of all restriction, and when the diseases had circulated (in the case of RSV at high levels) in the southern hemisphere, in their winter preceding ours.
But it does not account for why people are becoming more ill with these diseases (strep A and RSV, it's harder to call with flu as that's more variable, but it does seem to be making enough people very ill to be causing problems with number requiring hospitalisation even this early int he season)
Whereas temporary dysregulation of the immune system, especially in regards to diseases which would normally be tackled by the parts shown to be affected by covid (so not all diseases) would explain why a higher proportion are getting the more severe form of the diseases.
TLDR: yes, previous infection with covid could well be a factor.