How can I say that you are a pro gambler? You are stating by yourself on this:
For a couple of years, I had a lot of success betting on football from very obscure leagues. I had an algorithm which was great at spotting games where bookmakers had not priced up correctly.
What? I don't see any thing on that quote which supports your statement. OP mentioned that he became successful on sports betting and not on poker. Nah, nevermind.
He said:
For a couple of years, I had a lot of success betting on football from very obscure leagues
By saying that, I only think that he is a pro gambler because not many of us can get a lot of success betting on football

Perhaps, if he still stays with the betting on football and doesn't move to a poker game, he could get more money because he has much experience in that game. I only think that he wants to try with a new game and he choose a poker game.
But to be honest, the poker game is too difficult to learn as I try to learn, but I failed over and over, maybe it because I don't have interest in the poker game or maybe a poker game was really difficult.
football betting or sports gambling in general is more easier and more predictabe than a poker or card based game . so how can you say that no all gamblers became succesful in betting on football matches ? yes poker game is more difficult but it is also verry rewarding once you already grasp it . you can earn more fast and huge income but its also enjoyable at the same time when compare to football betting or sports gambling .
I can say that is because not all of the gamblers can get valid information related to the match. Besides that, gamblers can miss one or two things with the news so they cannot win.
That is true that football betting or sports gambling is easier to predict and all things depend on how we can get the information. But in a poker game, not all gamblers can understand about the game, and even they cannot win easier than in the sports betting.
I don't think that you can earn fast in poker games because when someone can win in the poker, he should have high skills and experience besides that, his opposite will also have high skills, so it depends on the luck.
Yes, I agree that both poker game and sports betting are enjoyable for the gamblers. But if you feel difficult to learn poker game, then you can go with football betting or sports betting because you only need to search valid information related to the game.
But to be honest, the poker game is too difficult to learn as I try to learn, but I failed over and over, maybe it because I don't have interest in the poker game or maybe a poker game was really difficult.
For starters it can be difficult but once you memorize the combinations it's not that complicated to play and win.
So at least, we should have a good memory to remember the combinations which not all gamblers can have.