Why as a country are we allowing this to go on

I live in the GTA. My friend is a landlord in the Brampton area. She rented her house out to a "nice elderly couple". Now 6 months later they locked her out of the house (changed the locks) and her 3 bedroom house has 25+ students living there. Neighbors have complained about noise, fighting, people urinating on the sidewalk. Fire department told her she will be held liable if a fire happens but she has to go through the long legal process of evicting them.

Shes doing everything she can to evict them. But its crazy how a tenant can take over and turn it into a housing for foreign students.