With the amount of violations I think there was just too much for the stewards. Each violation needs to be checked and validated because you know the teams sure as hell will do so.
I don't know how many people were doing the checks but let's say a single check takes at least 10 seconds of "eyes on" time. They reported about 1200 violations. That's 3,33 hours of only track limits violations. And I'm certain some of those checked took longer than 10 seconds. And that's before you get into all the other checks that needed to happen like "Unsafe release", "Forcing another driver off the track", and "not serving a time penalty correctly".

For a track limits violation it's super simple. White lines, keep at least one wheel within them. The fact that several drivers managed without a single violation means others were doing something wrong.