Does social media and mainstream presence, through interviews and publishing in the "trade press", help one's chances at tenure? One of our lab directors, on tenure track, has been active in the mainstream, e.g. doing science interviews on radio, tv, newpapers, and another researcher (post-doc, I think) has published in the "trade press" rather than in an academic journal.  

Does promoting your work in the mainstream help one's career in academia?  Will a tenure / promotion committee look favorably at one's popularity in the mainstream?

I'm asking particularly about large research universities in the United States.
In fact, in the absence of a large body of work published in quality academic journals and attracting loads of grant money, the strategy you mention will probably hurt your chances for tenure in large research universities in the US and probably elsewhere. 

Tenure is granted in such places by committees of peers, who are mostly grant funded researchers who also teach. But it isn't your external reputation that will be examined in the meetings of the tenure committee but the quality of your research and the number of times it is cited in scholarly journals. 

The above is not a universal and there may be exceptions, but not many. Your reputation outside academia is of little value in tenure discussions. However, once you are tenured (and funded), your visibility might be considered useful when it comes to salary negotiations and some expectations put on you (teaching, committees, ...). 

Visibility within the community of scholars within your field via presentation of work at scholarly conferences is a bit different, but it is backed by the research, of course. 

But if you want to be tenured at any research university, do a lot of research and get it funded outside the institution. The funding helps pay for graduate students who aid in the research, of course, and pay for labs, etc.