Assets sold to a third party so Barcelona have money now and right now.
This drastically reduces Barcelona's yearly revenue stream, and the deal is for about 20 years. They do have the option to buy the assets back in one lump some if they appreciate, but this would be a significant amount and would almost mean Barcelona would need to generate profits yearly + win major trophies.
All in all, they are relying on the Super League allegedly over generating profits yearly + win major trophies. They are in serious shit.