There was a range of issues in Ballymun - the design of the towers made them hard to maintain and eventually the council fell so far behind on basic maintenance that basic amenities like lifts were left not working.
Can you remember reading about the annual costs of repairing those lifts? They were jaw-droppingly astronomical - and, it was often said (off the record, naturally) by Dublin Corporation officials that a minority of the tenants made it their duty to vandalise them as soon as they had been repaired.