He had already been questioned by police in Sweden prior to that. He even stuck around for a month and then asked the Swedish police if he was free to leave, he was told he was.

The prosecutor dropped the charges because the alleged victims were quite obviously lying about having been raped using any conventional definition of the term, there was also no way to resolve any dispute about whether someone was asleep when sex happened, and they would never reach the level of "beyond reasonable doubt" by any jury as a consequence.

The charges were later mysteriously resurrected by a different prosecutor so he could be questioned again. Or maybe it's not such a mystery after all. Either Sweden is doing as the USA asked for some convoluted reasons, or the Swedish justice system is a complete joke when the R word gets involved.