Here we go again, second guessing HKB”H. There is no one among us who knows exactly what the reason for COVID was, and trying to make one up, even if logical, is a futile effort at claiming to be greater than one truly is.
The census is aimed at counting all people, and nothing to do specifically with Jews. So, stop it.
There is no exact count of how many people attended the Siyum Hashas. All we really have is a collection of estimates, with input of some numbers, and the people from both law enforcement and media who claim to have expertise in estimating crowd sizes. So these numbers do not matter at all. I have no way to know what caused the mageifa, and I do not think it is respectful or Torah consistent to claim that one does know. All we should be doing is to cope with the situation, and to self-examine to see where we can better ourselves.