CRANKCASE doesn't really care about MEGATRON; he just joined the DECEPTICONS because he was in a bad mood, and it's pretty much lasted. As far as he's concerned, everything is pointless and stupid. He sees no reason why anyone else should be enjoying things when he's so miserable. That's why he spends his time grumpily ruining things for AUTOBOTS and DECEPTICONS alike. He's not much of a warrior, so he specializes in just being inconvenient. His blaster arm causes metal to rust instantly.