Is it ethical for a landlord to kick a tenant out when a landlord is not able to rent an entire unit out?

I know one guy who had mildew in his room and construction came in. He had paid all his rents on time until one time when he had to spend his money to cover an emergency. Even though he had a loan that was approved and was willing to pay the late fees, the landlord kicked him out. However, when he went back to visit his old apartment he had found out it was still under construction. Therefore, his argument is that the management should have just left him in possession especially since the money was guaranteed.