The 100m sucks. People only care about it because the TV hypes it so much. They will devote 9 hours of broadcasting time to build suspense for an event that barely takes 9 seconds.
The event that people actually respond to on their own initiative is the 400m. In the 400, nobody has ran away with it by 3/4 of the way through. In the 400, things don't change in the blink of an eye. In the 400, you can take your time to watch all the runners and see everything unfold, without it taking too long and being boring. In the 400, you know they are tying up on the homestretch and anything can happen! Even non-runners can see them at their limit and can relate to it.
The 4x400m relay is beyond any dispute the most exciting and crowd-pleasing event in all track.
The 400 is the longest event that is never "tactical" i.e. boring AF and the crowd hates it and the TV cuts away to the field events.