It varies from person to person. I have seen both cases: when a person is winning, he becomes addicted, and when a person is also losing, he also becomes addicted. But in the long run, the winning isn’t constant. You have to face losses only; hence, in these cases, as the gambler has tasted victory and winnings, the addition develops more to gamble and convert the loss into a win. Generally, gambling addiction is seen in rich people, and they gamble to defeat their egos and hence get into addiction. Addiction is really bad, and each person has different reasons to get addicted.
Yes, it varies, I also believe that defeat can make a person addicted, but usually defeat is an annoying situation which means it takes up more emotions due to the inability to accept results that are not in line with expectations. And overall, in my opinion, the biggest trigger for addiction is winning, as you said, when gamblers experience victory after victory, their addiction will grow.
One of the reasons why addiction is most likely caused by winning is because it is certain that winning is a very encouraging situation which will indirectly make gamblers increase their hope and confidence that in the future they will be able to win again in even larger amounts, and so that in the end they become dependent on these activities, but on the other hand, in terms of addiction, to be honest, I cannot exclude poor people here, because whoever you are, if you are involved in addiction, it does not mean that it is impossible for you to end up with an addiction.