This is really sad, it seems there are already 3 accounts that were known can be trusted, have green trust and good record in lending history, but they still scam in the end. Is Bitcointalk account is worthless now since they're willing to run their reputation? I mean there are so many signature campaigns comes up, they can use that opportunity to make some money.
I don't quite understand it either, by defaulting on the loan they lose the opportunity to make money on that bitcointalk account, which is pretty stupid financially speaking.
Causes for them to do this I can think of is that they have other accounts on the forum that they are monetizing, but I think this is less likely, or that they are degenerate gamblers, or that they use drugs or something.
That in case they are participating in signature campaigns, although I think that in this case he was not participating, and it is not 100% clear to me why sashan gave him the loan, I guess because Devawnm367 had a previous history of having returned loans.