IMO there are two reasons why the 9/11 attacks resonated. The first one is crucial for the second.
The first is that it was spectacle, literally. It is impossible to deny that the image of a large passenger aircraft flying straight into a building and exploding is simultaneously nauseating, enthralling, and "better than fiction" in the emotional response it can get out of anybody. The second reason is that once cable news had that spectacle to get their viewers, it was like
for them. Just play it back. Replay it. Play it again. Run that another time. Get the second angle. Get the third angle. Play it again. Play it another time. The ad money coming in at that time must've been tremendous. It was really time for the fourth estate to shine. Judith Miller can tell you all about that.
COVID deaths? No spectacle. It doesn't matter that well over a million Americans died from it, as well as millions more globally (and we still are dying, too). It's undeniable that COVID had media coverage, but it wasn't like CNN was sending in camera crews into hospitals to catch people's last gasps of air before they perished. Abstract reasoning is too hard. We need to see the explosion and the building collapse, not reason about a number.