Helios was caused by the pilots misundertanding the cabin altitude alert for a faulty take/off configuration alert (same alarm). At no point did they suspect a failiure to pressurise and they never donned their masks, unlike the passengers whose masks dropped down in front of them.
No doubt had the masks dropped down for the pilots they would have got the message, but instead they messed around calling maintenance slowly becoming hypoxic until it was too late.
I wonder if any of the pax on the Helios flight were alarmed by the fact that nothing seemed to happen after the masks deployed?
If, as seems to be the concensus here, pax were aware of what usually happens in the event of a depressurisation event (ie sudden descent to a safe altitude), perhaps someone might have caused enough of a ruckus to eventually get through to the crew on the ill-fated Helios flight.