This is months after some of the biggest wikileaks releases including "collateral murder" and heading into the release of the Iraq War Logs and State Department Cables. https://en.wikipedia.org/wiki/List_of_material_published_by_...
Then a couple months later, based on no additional information, they reopened the investigation. He ended up going into the Ecuadorian Embassy soon after the release of "Global Intelligence Files" because the USA and private intelligence agencies were after him.
None of this has anything to do with the rape charges though. He is being sent to the USA over the 2010 Manning releases because he was communicating with Manning while she was stealing the docs. If she wasn't such an attention whore, she wouldn't have even been arrested. She bragged about it on IRC...