Someone who's put under a conservatorship can't tour, give coherent interviews or make important, public appearances in the way that she had not only shortly after the conservatorship was put into place, but long after as well, so we know for sure that she doesn't have any mental illness that would usually warrant a conservatorship.
Most mental illnesses have a terrible stigma. They're seen as character defining traits, when they're really just labels that doctors use to be able to treat patients better, so it's really no wonder that fans don't want to acknowledge something that isn't shown direct, reliable proof of. Britney has never shown any of the defining traits from the things she's supposedly been diagnosed with. She's never personally talked about them. Not to mention Britney has been falsely accused on legal records for having dementia, so being able to see what is the truth is getting harder and harder. It's important to read in between the lines.
I really feel like I've made my point. Her having possibly something like bipolar disorder didn't warrant any of this, and it's so far beyond the point that I really don't even see why you would want acknowledgment for that.
As for her doing weird stuff, she was a celebrity tormented by the world who wasn't being allowed to release her music and was partying all the time. She obviously didn't know what to do with herself.