Celestia instantly makes more sense as a character when you ignore the princess stuff and remember that she's a 1000+ years old wizard. Of course she does manipulative trickster stuff to teach moral lessons and/or cause chaos to amuse herself, that's classic wizard behavior. Of course sometimes she's actually socially awkward and bad at personal relationships and has bad ideas that she thought were good that result in her eating shit embarrassing style, that's classic wizard behavior. Of course she lets the aristocrats and nobles run around being assholes she's still running on wizard advisor programming, she's basically trying to merlin the entire upper class of equestria instead of just a king and some knights. "Yeah uuhhh we'll release the incarnation of chaos himself from his ancient prison because we think this shy girl can be friends with him", terrible plan if you're thinking like a ruler, amazing plan if you're thinking like a wizard. Just look at Canterlot 'Castle' for five seconds and ask yourself if that's in any way a castle. No. Wizard tower, yes. Wizard.