OP never used the word "character." They asked about good deeds, which appears to be about the action, whereas character is about the intention of the person. If MrBeast cured your blindness and he did it solely to make money and doesn't care about you at all, you still got your blindness cured. If I volunteer at the soup kitchen just to meet women, I have failing character but I still did the good deed. This is the MrBeast dilemma: what are we to conclude when the two are in opposition? What does it mean when someone does a good deed in order to benefit from it themselves? Is that a win-win situation, or is it bad? Does it completely negate the good deed? These are generally unsettled questions in our culture.

Based on the context they were obviously judging their character based off their "good deeds". You are just circling around the obvious. As for this "dilemma", he has already shown he will exploit children.

This tells you who he is and what his incentives are. If you would like to believe otherwise go for it. My advice simply is to watch out in real life for people you think are good if this is how you judge people.