The best part of that was that Kat, who Mundus hoped Vergil would want to rescue, meant nothing to Vergil. If it wasn't for Dante, Mundus would be like this:
Seriosuly, Mundus' whole plan to get Dante hinged on the hope that Vergil would care enough about Kat to give away Dante. Also, if Mundus did think Vergil cared about Kat, didn't it ever occur to him that Vergil would kidnap someone close to him as payback?
Then there's the whole thing about Mundus caring about his heir, and actually wanting an heir. The guy is an immortal demon king. Sure, immortal doesn't equal indestructable, but it's still a bit strange that he would want an heir when he could potentially live forever so long as the hellgate was in tact.
Also when Dante sends the return message with the exchange for Lilith...why did Mundus care? He could have just gotten another lady pregnant. Vergil did imply that there was more than 1 woman around Mundus. Heck, the way Lilith acted when Mundus mentioned the succubus made me think he was having a thing with that too.>_<
And good point about sending an army to Order HQ instead of SWAT. He could also have just bombed the place to bits as well.
It is one of those,
"HOW DID THIS MANAGE TO TAKE OVER HUMANITY!" moments that I will never understand
Relevant is Nostalgia Critic's review of Battlefield Earth