Inherently, nothing, but allegations do not equal guilt. However in Assange's case, the allegation was taken as fact before the evidence was investigated. Upon investigation of these allegations the case was dropped because the evidence was not strong enough. Witnesses memories had faded after 10 years.
Assange being in the Ecuadorian embassy would not have prevented Sweden from building a case and charging him.
The UK urged Swedish prosecutors not to question Assange in the Ecuadorian embassy,[1] though Swedish prosecutors eventually did so. When Swedish prosecutors wanted to drop the investigation, British officials urged them to continue it:[2]
> Don’t you dare get cold feet!!!
But immediately after the US began extradition hearings against Assange in London, and there was a debate over whether to give the Swedish or American request priority, Sweden dropped the case.
Just to top it off, Swedish prosecutors altered witness testimony[3] and UK prosecutors deleted emails relating to the case.[1]
The investigation was dropped because it had already served its purpose.
https://www.theguardian.com/media/2019/nov/19/sweden-drops-j...