And within myself, I am still wondering, what could possibly lead a person back to gambling after successfully quitting initially? Know well the reason for initially quitting was addiction, does it make sense to go back to gambling and become even more addicted?
OP, I don't think that your friend quitted gambling, he went on break and didn't quite. Gamblers are used to going on break after a huge loss because they feel that's the best way to avoid more losses. However, after a while, the gambler can start considering to gamble again in order for him to see if he can win back his losses. This is the reason why, when gambling don't think of profit in order to prevent you from making wrong decisions.
Indefinite break is already equivalent to quit the time he decided to stop gambling. We are just assuming that it’s a break now because he already returned despite stopping for a long time in gambling.
We do change and make our decision based on our current situation. That time he is so negative on gambling that’s why he decided but just return after acceptance of loses in the past.
Imo we are always encounter a scenario that we decide based on the heat of the moment and later on breaks it.