Gazza has an addictive personality. It could have been anything. Drink, Drugs, Pies or Pussy. He had the money to get help but chose not to get it. He had people who were there to help, but he chose to associate with the ones who were no good for him.
Much the same as the drunken gheyers you hang out with at the Well Hung Gun.
(There you go. It's not as if you weren't expecting it now was it?)