That's my take. While happily driving home with his big bag of money, he had to have realized he was caught on camera. There was no way he was going to get away with it. So he did what he had to do and turned it in. imo
“he had to have realized he was caught on camera.”
If he realized that, he wouldn’t have lied about where he found the money. The same would hold true. More likely, he had an attack of conscience. I don’t think he should be fined for it because in the end, his conscience won.