Additionally, a pandemic has shown that government services actually need to scale to arbitrary amounts, seemingly at random.

Don't you think that in this case using AWS is better to simply guarantee availability? Imagine tax payers money being spent on servers and then a pandemic happens and when the economy is screeching to a halt, more tax payers money is needed to expand the cluster, money that really would be useful to spend elsewhere.

true, but it's not in the business of wasting money either. if they don't take care about economic efficacy, then someday voters are going to judge them for wasting tax payers money