I used to generally think that a delayed flight helps your bump chances, mainly because all passengers will show up. A delayed flight (theoretically) means less misconnects and less people missing the check-in cut off and being denied boarding.
After a flight this weekend I kind of changed my opinion on that, though. I was trying to standby for an earlier flight which was literally zeroed out for a week beforehand. All of a sudden it posted an hour delay, and it went from Y0 to Y5 (meaning they were willing to sell five seats), and this was a 50 seater RJ no less!
Therefore I feel that delayed flights will generally hurt bump chances, at least in most cases, because passengers may reroute to different flights due to anticipated misconnections.
There are some exceptions, though, like flights to non-hubs where there aren’t typically many passengers connecting onwards. If everyone is going home they’d likely stay on the delayed flight, up until a certain point. That’s also assuming there aren’t many frequencies where passengers could standby on an earlier flight, although that’s typically not the case for non-hub flights.
Just my two cents, and something to think about for those like me that (used to) get excited about delayed flights that were showing as packed.