I really hate when I see stuff like this. It just shows the true nature of most humans. This dude literally begged this guy to come to the casinos with him, his friend turned out to be super lucky and always wins, but yet he loses. Its hard to not feel bad for the guy who always loses but he should be happy for his friend. That's like teaching your bud how to play baseball and him becoming a huge star and you're just stuck in the outfield and cant make any catches or help plays move along. Maybe its time to find a new game my friend. Gambling isn't for you. The universe is telling him something haha
In as much as this isn't so pleasing to see, it's just human nature playing out, it's only a few rare ones who gets genuinely happy for you when you eventually grow above the limit they have expected you get to, it's even worse if they no longer get better at something they taught you only to see that you keep getting better and improving much better than they have done all the times they have had an opportunity at that same thing. Like you rightly said, maybe this may not be his thing anymore and he's should go look out for something else but he's yet to come to that realization and going in terms with such.