I think it's because Marcus at some point in the film basically begins improvising because Khan takes his actions. He had an agenda that pre-existed but London and then the attack in San Francisco makes him change his plans a bit.
But what seemed odd to me was what Khan was expecting to have happen once he arrived on the Klingon homeworld.
'If the Apocalypse starts, beep me!' - Buffy Summers
'The sky's the limit.....' Jean-Luc Picard, 'All Good Things'
courtesy of Saquist