Cyttorack is an evil being and the last time I checked robbery and bullying are forms of evil whuich would fall under the category of something Cyttorack may want.
"Evil" doesn't really come into it. Cyttorack would be pretty evil by our standards, but mainly he just wants people to know how awesome he is. Doctor Strange himself has used the "crimson bands of Cyttorack" on multiple occasions to subdue his enemies. Robbing banks would be almost an insult to him. That's why in the X-Men one-shot of World War Hulk, Cain initially gets completely owned by the Hulk, but then actually brings him to a standstill when Cyttorack allows him access to more of his power.
In the end, Cyttorack doesn't care if you're a hero or villain. If you're wrecking stuff in an epic way and letting people know that it's HIS power that's letting you do it, he'll keep the juice flowing.