Time, pressure and a real investigation more than likely. They never did a real investigation in the week after the incident that they came to that conclusion.
You can bet dollars to donuts both Vegas and the PA have launched investigations, and filed grievances to the NHL. That process would undoubtedly take more than a week.
Interviews, documentation, precedence, all would be a long process.
NHL needs to lay down the hammer, and it can’t be monetary, otherwise, what’s stopping other teams from doing this (Central registry obviously should be implemented, but alas…).