The making of CNN was Desert Storm. They covered it better than anyone else. There and then they hooked the 30-40 demographic of the time and exploded. They've lived off that reputation for decades at this point.
Doesn't CNN still have more reporters world wide than any other US based news org? I imagine the BBC has the most when comparing news orgs around the world.
I think this is why CNN still gives better news coverage than other stations, but the opinion shows drown a lot of that out.
Don't forget about the captive audience in airports, too. That kept CNN artificially in the public eye.
Zucker rationalized the decision by blaming streaming services and other mobile media but I don't buy that because Airport was still invasive - i.e., people look up from their devices and could still be seeing CNN, etc. today. And, from a business perspective, it required very few internal technical resources (a single master control system and operator) so the costs were almost certainly exclusive to whatever fees CNN paid to airports to install their receivers and displays.
(Full disclosure: I'm a former operations-level CNN employee, half speculating from my time at CNN WHQ)
Like that time they interviewed Osama bin Laden right before the 1998 Embassy bombings to make sure the public knew who he was: https://www.youtube.com/watch?v=orawG7vt68o