I think /u/celebreth answered this best from a couple of years ago: https://www.reddit.com/r/AskHistorians/comments/2r8597/was_caligula_crazy_subquestions/

Long story short most of the texts written about Caligula said he was extravagant (which archeology has evidence for) and crazy. However they were written by mainly people who hated him and they may have amplifed his eccentricity up. But solid evidence of being a depraved monster is lacking.

To piggyback on this question - I had read somewhere that the reason Caligula was depicted as insane and brutal was due to later historians trying to discredit him and other emperors. I know I've read that his attempt to make his favorite horse a consul has sometimes been theorized to have been either a prank or an act of contempt to the senate.

So is there any consensus as to whether Caligula was brutal and insane or just hated by later politicians and/or historians?