I'm not sure why you think it is rational to take the "sure bet" if you only get one chance, but leaving that aside, there is a much, much bigger problem:

When the gamble is posed as a gain (lives saved), people take the safe option. When it is posed as a loss (people dying). But it is still the same problem. That is the behavior we are trying to understand.

There are a lot of good suggestions out there, some in the comments to this blog, but I don't think the fact that people are treating it as a single occurrence is going to be sufficient by itself.

Please try my web-based experiments