Because the deal saddled WBDisco with $53 billion in debt.
That's right- the net leverage of WB is over 5x (Disney's, for comparison, is at 2x-2.2x). So HBOMax is in a weird position- it isn't a subsidized service (AppleTV+, Prime, Peacock, even Disney+) that can just funnel money into streaming in the hope of future profits. And it's not an established, powerful, and profitable player like Netflix.
And it has a massive debt that it has to service in a time with uncertain, and high, interest rates.
So now look at all their decisions-
Batgirl? Save money.
Removing big shows from the platform? Save money.
Going in a new direction in the DC Movie universe (and not paying established stars)? Save money.
Getting rid of high-concept and expensive shows in favor of more Dr. Primple Popper? Save money.
In other words, it is a company with a crippling debt burden looking for a way out. Maybe that will be a sale, or maybe that will be a continued pivot to a lesser version of what it once was. But when looking at any decision made by HBOMax (or the parent studio), don't think of it in terms of creative decision-making, or the fans, or even the future of the company ... just remember ... 53 billion in debt needs to be serviced.