Its about taking the least chances.You can payup 600k when you still have access to millions and have it forgotten about in a day, or you can risk some gang war that might get you killed.People nearly always choose the soft option.Tyson was a sportsman, not a gangster.
Boxing isn't a sport in the same way tennis or golf for instance is. Boxing is a violent sport that tends to attract unsavoury characters who are linked with the underworld. Many boxers have been ex-gangsters themselves or have served jail time.
Mayweather for example is a sportsman but I'm sure is far more connected with dangerous individuals compared to top athletes in other sports. I find it difficult to believe Tyson would have passively accepted being threatened by a thug and just let it go. It's not as if Tyson was a reasonable and thoughtful person too. He was known for his often volatile and erratic behaviour, even in the ring.
I think anyone who tried to get aggressive with Tyson would have paid a price. That's why I find the story difficult to believe.
Darren Avey tends to tell a lot of tall tales.