- The gambler being so poor and have not seen such amount in his life, so he couldn't handle the reality of having such money, hence the shock killed him
- He might be sick such as being hypertensive so the shock of the winning triggered the sickness
Most likely it's the second case, he could have been sick already and he might have felt it before, but he just ignore the signs and so when he win big, it triggered his health issues causing him to collapse and then later die and never see the huge win that he had won.
Hopefully, he was able to cash it out and his family can used that money for a proper burial. This is just one case that might really be the sad reality for every gamblers. And we should really be prioritizing our health as well and have checkup first before we used that money to gamble. Otherwise, our families are going to grieved by this very sad story of winning big in exchange of your life. And they can only wish that you didn't gamble and win.