Doesn't sound too unusual. They were hired to paint, not maintain the garden. If the landlord didn't ask them to watch out for the garden they won't care much. They'll only be interested, really, in the directions of whoever is paying their bill.
When the roofers were done at my place, they removed all of the ground cover and mulch I'd been developing in my front garden for 4 years. I was p!ssed, but I'd not talked to the guy who did the quote about the ground cover. My fault.