I can see how it looks horrendous at the end of the let. They do not appear to have taken reasonable care.
But I could also see a scenario where they turn up, one of the couples sets up in the studio because no one wants the 9-year-old boy to be sharing with the adult couples and there's supposed 4 bedrooms plus a garden studio with a day bed in there that converts to 2 singles or a double bed - it's why they booked the place. So they try to get it to convert, but they can't work it out, think they've got it and then something bends/snaps/breaks and they can't even use it as a sofa anymore. They upend it to make more space for their mattresses on the floor and are really annoyed at this supposedly luxury place they've rented. Then they can't get the hot water working for two days. End up feeling like idiots when they find out why, but they still spend two days before that annoyed that the there's no hot water and on top of the bed it just feels like they've rented a lemon.
The TV is in a position where it gets hit by the sun so they can't see the picture or it's not in a place where there's enough seating for all 9 to see (or they're dicks and want to move it so they can watch while they BBQ and swim in the pool), they're already annoyed with what was supposed to be a luxury holiday so they move it to somewhere more suitable, hence the plugs being pulled out of sockets so they could move it somewhere convenient, hook it up to their laptop (which is not what I imagined you meant when you said wires pulled out of the wall).
The pool pump appears to stop working - they' don't have a pool of their own, know nothing about it really, but are worried about it wrecking the rest of their holiday because then the pool won't even be available and they're already thinking the place is poorly done - so they call. The minute they sit down on the sofas in a waterproof sunscreen (pretty much a standard expectation in a villa with a pool) the cushions get stained. The place looks and feels a mess by the second day and they spent, to them, a fortune on the holiday. They are annoyed at you.
Lots of other little things don't meet their expectations and they end up really not caring by the end of the holiday. Leaving everything a mess.
You think they are bad guests and they think you are a bad host.