The thing is, there's a large exhibition hall that can get 12,000 in. A stadium bowl that can accommodate 40k for concerts. There's a hotel onsite which has less than 200 bedrooms (I think - memory not what it used to be).
The ratio of bedrooms to potential visitors to events is stupidly low. Any new hotel would be built to help attract larger multi-day conferences, exhibitions etc as there's more bedroom stock to house them. As it stands, I'm sure the Arena misses out on a lot of business due to insufficient amount of bedrooms near the venue.
As for the rest of the time when there's no events on at the Arena? The location means it would be a decent stop for transient business travellers although transient business travel isn't what it was pre-pandemic. Add on social events like weddings, Xmas etc, there's definitely validation for one or more new hotels on the Arena grounds.