The man probably trusted his family, which is a really natural thing to do, though sometimes it turns out to be a mistake, like it clearly did in this here, as the son proved untrustworthy, unfortunately.
Trusting your family is natural, but it's also not without risk. We don't know what people think, not even our closest ones or family.
Some people usually when they want something they will do anything to get it, including crime.
Yes, sometimes money blinds everything, we don't know who, when, and where people will be mean to us. May this be a lesson for all of us.