They are donating and posting their confirmation mails on pr0gramm.com. The servers cant keep up with the amount of donations.
It would still be a bit sad if a cancer donation site could be brought down with so much less than 1 donation per second, but I'd use occam's razor.
Still we don't know if that brought down the server accidentally or on purpose. It's a question of intent, and their desire for publicity. Sadly, it only takes one.