Some diseases are more infectious than others. Breathing in a single virus particle doesn't necessarily lead to becoming infected. Instead it's a numbers game, with the degree of infectiousness of the virus combined with how much you inhale (or ingest, or absorb, or whatever) determining your chances of becoming infected.
It is believed that difference strains of the COVID-19 virus have differing degrees of infectiousness. The early strains were less infectious, but a mutation increased the number of "spikes" on the surface of the virus, increasing the likelihood of it penetrating into cells, and so making it more infections. There were a number of posts on this thread about this several months ago. The strain of COVID-19 virus that first turned up in Wuhan for example is believed to have been much less infectious than strain hit Italy.
I understand all of that. The graph that was posted appeared to show flu had totally disappeared after April. I thought I was quite clear that I would expect a decrease in flu deaths with all of the factors involved (less interpersonal contact, mask wearing, social distancing, vulnerable people dying from COVID etc.) but for flu to disappear totally was not plausible.
That graph was showing 'sentinel' cases, not total cases as I've stated before. The same pattern is seen every year. It's not a COVID effect, it's an artifact of a very limited sample and a seasonal disease.
My point still stands, influenza and COVID are spread the same way. If methods are effective at completely eliminating one disease then they should eliminate the other at the same time. That is not the case and both diseases still exist in the population.
Edit - to put it another way, the current measures would probably have reduced the incidence of smallpox if that was still a disease in circulation. The graph posted that I responded to would appear to suggest there were zero smallpox cases whereas in reality it would show that fewer than 5% of doctors had seen a smallpox case.