From what I understand, the agent didn't gave 8k at one go but he gave small amounts first. The agent didn't hope for the bettor to win but what he only want is for the customer to pay on the designated dates. I don't think the gambler don't consider the risk of losing because he just lost earlier but indeed he was greedy. At that time, he is only thinking for a revenge but unfortunately, it didn't end up well.
The agent is only doing a business here or a kind of side job by letting the customers take a loan and the bettor in the story is only just a victim. None of them can be blamed but it would be inappropriate if the gambler will ran away for his obligations.
The gambler priority was only to avenge his losses earlier, afterall he recorded gigantic losses, in my opinion the betting agent has no idea although he made faults because he knows the risks involved in gambling and still supports someone to gamble after witnessing the gambler losing steadily. They're both at fault, before gambling, atleast know the amount of losses you can take in and never to be too desperate to bet on games, do take time and mapped our good strategy, and if it doesn't go as plan, leave it, tomorrow is another opportunity to try again.