Why was Julian Assange not questioned in Sweden in the autumn of 2010?

The reason is that he was not available for questioning.

During September – October 2010 the prosecutor made a number of attempts to question Assange in Sweden, but the attempts were not successful.  During the hearings by the British court, the City of Westminster Magistrates' Court, with regard to the extradition of Assange to Sweden in February 2011, this issue was dealt with thoroughly, with support from and not limited to evidence of SMS conversations between Assange's then lawyer and myself. See the decision from this case (sides 9-10, points 7-15).