If this is a claw foot tub, at one point they had pins or nails in sideways slots preventing the feet from sliding out. At work a older home we are getting ready to open , in what will be the staff bathroom it had a claw foot tub, the tub needed to be removed to do the flooring , the feet were held into some grooves by SQAURE nails ( YEAH that old) ,the nails as well as the underside of the tub have alot of rust on them. Take a good hard look , if what ever was used to pin the legs in place was rusted OR the slots the legs slid into are rusted to a point of reduced support then its easy to imagine the tub partially tipping, IF you find parts that are severely rusted did they rust thru getting very THIN ? If both legs and the slots they went into were relatively free of rust and had SUPER clean cracks , (take pics ) yeah then I too would think the tenant did something to cause it. ITs possible the tenant didnt do anything out of the ordinary other than use the tub as it was intended, Take a good hard look at the tub before saying another word to the tenant about who is responsible for the repair.