Sounds like a painful travel experience, and sorry it happened to you... but as @
jrl767 pointed out the forum members on the Delta forums might be a bit more familiar with the policy of who gets bumped and how.
I know with AS, one of the factors of who is the first to get involuntarily bumped goes by check-in/confirmation order... so the last people who were checked-in are more likely to get bumped. Given the crazy state of affairs it seems likely you were probably among the last people to be put on that flight, and if it was over-sold (or in over demand due to cancellations in this case) then that seat was probably double booked.
It'd be naive to think that airline status & revenue cost of ticket also don't play a role in bumping decisions... but again, that's just speculation on my part.