Why are you all assuming that the crew did not inform the pax of the reason for the delay?
The fact that a person is willing to open an emergency exit and try to climb down off a wing strongly suggests that he was not acting rationally.
There may well have been a PA or a sequence of PAs from the flightdeck and Cabin Crew which were either not heard or were not understood by the pax generally, or this specific pax.
I was once stuck in a UK airport after arriving late. We could not disembark because there was no ground crew, no chocks and no open terminal door. The aircraft on the stand to our right then started to board through the hitherto closed terminal door. Aside from chasing the handlers every few minutes, I made countless sympathetic and apologetic PAs explaining carefully the reasons for the delay. That did not stop a well-spoken English man who had presumably the faculties to hear and intelligence to understand the reasons for the delay, from standing by the open cockpit door pouring personal abuse on me for what he regarded as an unreasonable refusal to allow him to disembark and wander around the apron. If a man like that could act so unreasonably whilst in full receipt of the reasons for a delay, why are you quick to assume that no PAs were made?
And on countless other occasions I have made a number of explanatory PAs to pax only to receive a ding from the Purser to inform me that pax were getting angry and couldn't understand why we hadn't departed or disembarked. Equally, I had a flight last week to Copenhagen where a note was passed to me from a disembarking pax to thank me and the crew for a lovely flight. There were thanks from most other disembarking pax and no complaints. We were over an hour late and I had carefully explained the reasons throughout the flight. So, I agree, keeping people informed can work - but sometimes pax do crazy things or ignore everything said to them.
What you have to understand is that airlines like Ryanair carry vast numbers of pax who do not speak the language in which the PAs are conducted; they do not listen to safety demos; they routinely stand up and try to disembark before the aircraft is even on stand.