Because the writing and the gameplay are constantly trying to out do each other on how terrible they can get before the last player leaves. At this point fan fiction or even Goldshire ERP has better writing.
The craziest part is that the city of Stormwind is entirely covered with gryphon riders. You cannot approach from the sky at all without having a shit load of eagle lions clawing at you. And they didn't even give chase.
Warcraft's lore, logic, continuity and common sense was thrown out the window year and years ago. It's sad really. Blizzard ruined retail, so they launched classic.
Then the players proceed to ruin classic. Blizzard and their playerbase pretty much deserve each other.
Or they're a bunch of big baddies that could have just stomped into the castle, killed everyone in their way, and abducted their target that way. No pussyfooting around. But that would require re-texturing of environments and an event. It's just lazy storytelling. Thanks Activision.
From what little I'm hearing about this event, yeah. Lazy storytelling. Either the abductors put enormous effort into planning the perfect crime with inside information to execute it, meaning their weak opportunist (which they appear not to be)...
I mean, from looking stuff up, most of the leaders were stolen (like, all the ones they camera past earlier on in that cutscene video), we only get to see Anduin actually be nabbed. My guess on why it hasn't happened before is because this is the first time a bad guy attempted it with magic chains.