re: Was Caligula truly mad? Was he really crazy?

I think the craziest actions attributed to him were exaggerations by his rivals to tarnish his legacy, such as him allegedly ordering his troops to march against the sea and to collect sea shells. One theory is that when his armies reached the shores of the English Channel, they mutinied and refused to cross and invade England. Since he could not afford to "decimate" his army (the traditional Roman penalty for a mutiny was to kill one tenth of the men), he agreed not to invade Britain, but forced them to collect sea shells as a shaming punishment for their insolence.

As for his apparent blood lust, to me, it just seems like brutality with a purpose. He was doing what he saw as necessary to hold onto power, and in most cases, it was absolutely necessary. That's just the way Romans did things back then.