Good post. I think a lot of landlords, including myself, have been guilty of this to some extent at some point in our careers. Obviously this was an extreme case of letting stuff getting way out of hand. I think it's the fear of not wanting stir the pot. Some tenants cause problems, but not enough where you want to go through the headache of either finding a new one or take on the cost of an eviction.
It's not that you don't know what to do. You just don't want to deal with the costs associated of those actions and take the path of least resistance. At least you thought it was the easiest way forward until something else happens. By then it's too late and the tenant caused more damage than if you had acted earlier. It's not until then you learn the error of your ways and that you cost yourself more money, time, and stress.
I think COVID taught a lot of us the importance of tenant screening and not letting issues fester.