That "quickly" is on the order of years (as opposed to decades, centuries, etc). If the Starlink constellation goes boom, you can't start launching new ones for several years -- and then the build-up would take years, from there.
Nah. In any major future conflict, the combatants will go ahead and launch replacement satellites immediately regardless of the risks or long-term consequences (or they'll do it at least as long as their manufacturing and launch facilities survive). A constellation of hundreds of satellites can't go "boom" all at once. Even with a bunch of orbital debris floating around the hazards will be sparse and some satellites will live long enough to be operationally useful.
Nah. In any major future conflict, the combatants will go ahead and launch replacement satellites immediately regardless of the risks or long-term consequences (or they'll do it at least as long as their manufacturing and launch facilities survive). A constellation of hundreds of satellites can't go "boom" all at once. Even with a bunch of orbital debris floating around the hazards will be sparse and some satellites will live long enough to be operationally useful.