ceiling water stain cause

https://accondensateleakceilingnews.greyhavendaily.com/posts/how-to-spot-an-ac-condensate-leak-on-your-ceiling-vs.-a-roof-leak

That ugly brown blotch spreading across your ceiling is usually from a slow leak above - maybe a worn pipe joint, a loose roof shingle, or even a clogged AC drain line sending water seeping through the drywall.