I suspect Caesar's dropped DEF CON because the DEF CON attendees likely have a fairly low "avg revenue per attendee" yield because fewer of them gamble compared to the avg Vegas conference attendee. They also probably spend less on high-end restaurant dining and bar drinking inside the hotel.

Since the pandemic Vegas has had a pretty strong resurgence in general and this may be a sign that Caesar's is doing well enough they've decided there are higher-revenue guests they can put in those rooms — even in the doldrums of August (a traditionally slow month for Vegas tourism).

I happen to regularly attend an unrelated, non-tech conference that's always right around the same week as DEF CON. That conference also happens to attract attendees who don't gamble or spend much at the hotel other than room costs. The reason the conference organizer chooses August is they get better discounts on their costs from the hotel in exchange for filling up rooms that would otherwise be empty (except this hotel is lower-end and cheaper than Caesar's). This works out because unlike Caesar's this hotel is far off the strip and doesn't have nearly as much dining or gambling revenue potential anyway.