Zaslav has had some good ideas in his run (he's basically left HBO alone, I don't think he's diluted the brand, plus he's a fan of theatrical) but overall I agree with @Cmasterclay that he's just not been a very good CEO. Unsettling the creative community with the Batgirl cuts without giving anyone a phone call, foisting an albatross on De Luca with the De Niro mobster movie to impress his Hamptons friends, hyping up the Flash to unrealistic levels so that "pretty good" reviews ended up disappointing, riding CNN down to historic lows in ratings and relevance through an ill-conceived pivot-to-the-middle, these were all completely unforced errors that ended up damaging some key part of their business, to say nothing of the times when him or his team just embarrasses the company (e.g. Max "creator" credits). And while I didn't love the name HBO Max, I'm really not convinced of the logic of making another confusing rebrand just a few years after launch. It's not great that after a week, only 70% of people signed up.
He's a financial wizard but he's not a content or branding or vision guy. His brightest idea is, what, a ten year reboot of Harry Potter? And when WBD is finally sold for scraps to another company, the best we can hope for is that he'll take his big sack of cash and ride off into the sunset.