Qatar's causes tend to be "pro-western", so I dont think its that (unless, of course, there is a "Western" cause to which he was contributing, but then why not just quietly hand over the cash at the door of his lavish palace/rest-house?).
I was told by a friend in the civil service that large amounts of cash are standard with these people. They pay everyone in cash, they throw cash at the high-end prostitutes they bring in to dance at the rest-house, they tip lavishly...still, it does seem like a lot, so who knows. Maybe it was meant for some anti-Iranian group? and maybe this is not a way to hand it over, this is someone in the opposition (the jihadi faction of the ISI?) getting wind of it and arranging for the donation to be rerouted.
Who knows.
or rather, whoever knows isnt likely to tell.
But my default assumption is robbery and a prince who was carrying way too much cash.