Coincidentally I was on a Ryanair flight very recently about to start, APU whining away in the background, when it suddenly wound down and everything went black. I mean everything, not even the emergency lights. Most unusual. Glancing into the flight deck that too was dark. After a bit there was some lighting but no air. This was at a Spanish airport. It got very hot, very quickly, indeed the woman beside me commented that she felt she could hardly breathe such was density of the air. I felt the same and from the reaction of others around me there was a bit of disquiet. I turned to my wife and assured her that they would probably plug in an air cart and that duly happened, coolness was restored.
An Engineer appeared, entered the flight deck and started pushing buttons and soon whatever the problem was went away. The British Captain then came on and explained it was a 'serious technical issue' We left late but curiously arrived on time.
But whatever, being left in the dark, with that heat, even with the doors open made quite an impression. So it's understandable that someone took things into his own hands after an extended period sitting there slowly broiling with minimum explanation from the flight deck.
At a minimum there does seem to be a failure on the part of the crew to keep the passengers reassured. But I also think it would be wrong to simply suggest it's just a Ryanair thing. It could easily happen in other airlines.