I went down a rabbit hole last night (by searching 'Britney Spears' on the Crazy Days and Nights blog site).
I think that prior to the conservatorship, she was in such a mess that nothing else would have been as effective in turning her life back around. She had a number of hangers-on who were taking huge advantage of her, she was haemorrhaging money, and was fast on the path of self-destruction.
Her father went too far with it all, and I don't think he - or indeed any of Britney's family - has her best interests at heart, but I do think setting the whole thing up initially needed to be done. It should never have gone on for this long though.