I'm not a biologist, but that probably hits the nail on the head, though judging by your comment I think you meant k-selection, and it's actually r-selection that pertains to the "spray and pray" approach to offspring. [1]

There's also likely some luck involved that the initial two on that island happened to be viable colony starters.

[1] http://www.bio.miami.edu/tom/courses/bil160/bil160goods/16_r...