Bally's was up for sale (the buyer went with the Tropicana instead). Caesars then unexpectedly took it off the market. I guess because they had to put the WSOP somewhere. The Rio has already sold, so moving the WSOP out is just good business, as Caesars stood to make very little money.
With the WSOP moving dates around, it's possible that The Forum was already scheduled for another conference pulling in more money than the 8-Ball tournament. I still think the WSOP Bally's/Paris move will be temporary until it moves to the Forum.
...but in the end Caesars will put it wherever it is cheapest, because they are some penny-pinching, no-customer-service bastards. Your comfort is secondary to their profit.