Even the best due diligence can't do anything if a crisis (not necessarily banking-related, a Middle East might just do the trick) starts manifesting itself and now many of those businesses have issues in paying down the debt they owe.

"I did my due diligence but didn't anticipate these risks". Doesn't sound like due diligence to me. Not having a plan to unwind your position if SHTF doesn't sound like due diligence to me. You can argue it any way you like but it boils down to "The money was good and I didn't think the worst was gonna happen".