I think the bank does not have a legal obligation to honor the contract between then previous owner and the existing tenant. Moral obligation? Maybe but a lot of businesses now-a-days seldom put emphasis on moral obligations. I think with in the case of fafa Boybi, yung building eh na-elit i.e. kinuha nung banko from the previous owner na ginawang collateral yun. So, kung yun lang ang collateral, the bank has no choice but to take ownership of the building. The bank would rather be able to collect something than nothing at all.