Everything was in Valerie's name because Phelan put it there so that he could declare himself bankrupt and not pay any money to his creditors.
Phelan and Valerie didn't have any children as far as we know, so the starting point at divorce would have been 50/50. If he ended up with nothing, perhaps he did treat her badly and the court awarded her everything. (Though to be fair, marriage/divorce laws are the last thing we expect a realistic depiction of in soapland.) We do know she'd been turning a blind eye to him cheating for some years; as I recall, Valerie wasn't bothered when Anna tried talking to her.
Some offenders do have families who are completely unaware, because they're good at putting on an act. Phelan may only show his true colours when someone says no to him, if this turns out to be true.