When a virus kills off too many people it infects it's self-limiting from the start unless it has some way to continue transmission despite dead carriers, which is an alarming thought because it is one of the only ways any zombie nonsense would ever make any sort of sense.
COVID killing so many people while leaving the vast majority alive and able to keep spreading it is "better business" from the hypothetical perspective of a virus trying to continue replicating itself.
It's also less of an issue if the virus merely weakens a host possibly for life, as long as said host was able to pass the infection along, and while death is scary, long covid feels a bit scarier and is yet another reason I'm fully in the "don't fuck around, avoid it at all costs" camp.
Regarding the pardon thing, Flynn losing the ability to refuse to testify about Trump on 5th amendment grounds? Fucking hilarious self-own by Trump there, love it.
As for future pardons? I've never encountered someone seriously suggesting this was remotely possible, though I've seen numerous lawyers explain the whole "at any point after the crime, regardless of it being discovered/charges filed/conviction gotten, but any continuing criminal activity, even if exactly the same as previously pardoned for, is a new crime and not covered by said pardon" distinction with various sources from relevant cases testing the otherwise few limits on the pardon power.
Saw an interesting take on the wording itself, because it doesn't say "may pardon anyone" like one might expect, it says "may grant a pardon" and granting something to yourself is a hell of a linguistic kludge.