Except in this case it was senior prosecutor that dismissed the case initially, after having been in her own words extremely surprised at the unusual manner the police had treated the case in, including a number of irregularities in the interviewing (such as not recording them).
Yes, it is possible that it was "just" public scrutiny, but Occam's Razor is a guideline, not a law of nature - less likely things with more convoluted explanations happens all the time.
It also runs into the question of why this has not happened more regularly, given that Swedish media regularly gives copious attention to outcry over rape cases that don't get pursued.
Sweden has an amazingly high frequency of reported rape cases. It would seem odd if this prosecutor does not have a long string of rape cases with much more serious allegations to look at, rather than stepping in to take over another senior prosecutors case and spend massive amounts of resources on a case that she herself has been conducting in a manner that virtually guarantees that she on her own accord will not be able to move the case forward anytime soon.
If we do accept that it was more public scrutiny that triggered this, how do we explain why she doggedly insists on not questioning Assange, while clinging to the outright lie that she can't question him abroad (as pointed out over and over again: Swedish authorities do this all the time)?