User blog comment:Stormjay Rider/Not one, but THREE review results..../@comment-5955017-20131023203950/@comment-5955017-20131024015740

Here is the link to the Space Troopers project: in the description he said it was a theme.

http://lego.cuusoo.com/ideas/view/5127

Not that Lego couldn't have just released one set, but it would be a shame to get only one considering the themes wide array of possibilities. The new molds might have contributed as well.

Same with the Portal: while one set could have been done, it would be rather  disappointing not to include the other sets.

http://lego.cuusoo.com/ideas/view/18258

I guess the 'not releasing multiple sets' has a reason: fans might only like one or two and the theme would be a complete waste. I hope in the future that they will consider theme releases though: a lot of these projects had some real opportunity.