First off, why did he agree to give you 10% of the earnings? Did you help him place any of his bets or was it because he just didn't want you to feel left out.? At the end of the day your very friendship might be riding on this $140 that you now feel entitled to because of his half promise and unwillingness to pay.
It's normal in male friendship, you don't have to help anything, but they will give promise if x then I will do y. Hence, we have heard so many women saying men only give promise, but zero action. This one is the example, @OP's friend promise to give 10% of the profit, but he didn't do it.
Yes, it can be concluded that his friend forgot him when he was on top and remembered his friend again when he was down, yes, OP should be grateful because with this he no longer needs to respond to his friend in any situation, he also has to act indifferent to his friend so that his friend also realizes his mistake.
For me, friends play a very important role in my life if something happens, one day I will definitely need their help, so as much as possible not to break off friendship just because of money.
The reality is high class people tend to not help low class people and low class people tend to help other people. If you care with "friendship" you're high unlikely be rich since you value friendship over money, rich people don't have friends, but they have colleagues, acquaintances, schoolmates, clients.