Then factor in not only the monetary loss, but the sense of betrayed trust or loyalty directed at the possible whistle blower.
I would not be surprised if every biker club, fraternity, sorority, sports team etc. has some members who invest disproportionate amounts of their self esteem, money, time into the group.
These same members also derive disproportionate amounts of their social standing from the group and can takes things like real or perceived betrayal of or disloyalty to the group, well..... "more seriously" than others.
Though I am not comparing biker to Greeks directly, at their core, both are groups of humans who pledge to support each other and then spend alot of time and money doing so. This can generate similar expectations.
My fraternity (Sigma Omega Lamda Nu- Socially Awkward Library Nerd) did not permit much contact with Greeks. I do, however, remember one fraternity on my campus with a reputation for being "rough around the edges". Members were rumored to engage in night club fights, and known to aggressively intimidate student referees at intramural sports.
Perhaps such a fraternity could have a larger number of intense members? To paraphrase a famous police saying: "The murderer only needs to have a motive. It does not need to be a good motive".
Even still, and as you imply, it seems like a stretch. But... somebody had a motive.