Because it was a shady "character assassination" attempt without real standing in the first place...
"*The woman of whom Mr. Assange is accused of the offence
of "lesser rape" (a technical term in Swedish law) sent an
SMS to a friend saying that she "did not want to accuse JA
[of] anything" and "it was the police who made up the
charges". The other woman tweeted in 2013 that she had
never been raped. Both women’s testimonies say that they
consented to the sex. A senior prosecutor already dismissed
the ’rape’ accusation, saying that there were no grounds
for accusing Mr. Assange on this basis. But a third
prosecutor, lobbied by a politician who was running for
attorney general, took over the investigation and
resurrected the accusations against Mr. Assange.* [1]"
That's what happens when you mess with the big powers (and of course it doesn't stop to the "politician who was running for attorney general" being a single bad apple).
[1] https://justice4assange.com/