The managers don’t want a fight so they’ll just give them what they want so they leave.
Unfortunately, this contributes to the problem. It’s a reward for being an asshole. I don’t blame managers or staffers for giving in just to get rid of the asshole because it’s not worth getting screamed at. But it’s like the “customer is always right” approach devolved into “being an asshole gets you free shit”. I wish corporate culture was “treat our employees well and we’ll treat you like a king, be an asshole and you’re banned for life” or something along those lines.
Also, your money recommendations are on point and OP should definitely do some smart saving while they have the extra cash. It’ll help them out a lot later in life.
That seems like a pretty solid approach. It still rewards the asshole, but calls them out on it without being rude and commits to not letting it be repeated. I don’t think screaming at someone over a missed fast food order is ever warranted, but I think it’s reasonable to be extremely charitable and give the person a chance to recognize and learn from their behavior.