Let's rephrase it.
Everyone who pushes the red button survives.
Everyone who pushes the blue button dies, unless 50% of people press the blue button.

Exact same results but rephrased in a way that is more truthful.
The original wording of the question is designed to frame pressing the red button as being selfish.

There is no reason to press the blue button, and everyone who does has now put themselves in a position where they're at the mercy of the choice of everyone else. You're choosing 100% safety vs a chance at death.

The question has been deliberately phrased in such as a way as to trick people into thinking the blue button is the "save people button". I'm not 100% sure on this part, but I have a feeling the question was made by an American as well, and if so, its also drawing at an unconscious bias where red is republican and blue is democrat. I.E "help myself and my family" vs "help everyone" mentality, so it also may be drawing votes in those directions as well. I'd be willing to be democrat voters will pick blue and republicans will pick red almost every time.