Reading this (pdf)
SUPPLEMENTARY CONVENTION ON EXTRADITION BETWEEN THE UNITED
STATES OF AMERICA AND THE KINGDOM OF SWEDEN
TIAS 10812 35 U.S.T. 2501; 1983 U.S.T. LEXIS 131
March 14, 1983, Date-Signed September 24, 1984, Date-In-Force
If the extradition request is granted in the case of a person who is being prosecuted or is serving
a sentence in the territory of the requested State for a different offense, the requested State may:
(a) defer the surrender of the person sought until the conclusion of the proceedings against that person, or the full execution of any punishment that may be or may have been imposed; or
(b) temporarily surrender the person sought to the requesting State for the purpose of prosecution. The person so surrendered shall be kept in custody while in the requesting State and shall be returned to the requested State after the conclusion of the proceedings against that person in accordance with conditions to be determined by mutual agreement [*7] of the Contracting States. "
makes clear why no-one in their right mind (once properly informed rather than relying on what cognitive scientists refer to as 'folk' understandings - eg folk physics) would agree to go to Sweden on the doubtful grounds that Mr Assange is being sought by the Swedes.
Unfortunately for the Americans the United Kingdom has judicial processes that have to be gone through on extradition requests. Sweden has Executive decision-taking for the 'lending' of a prisoner for any period the contracting states choose at any moment of the Swedish state's pleasure. Short of extraordinary rendition (which when practised in Milan made the Italians very cross indeed and has led to a fistful of US agents now permanently excluded from Italy on pain of instant arrest and prosecution) Mr Assange had to be delivered to a more 'appropriate', a more 'yielding' judicial environment for transfer to America.
In these circumstances Angels would have nipped smartly into a friendly embassy too.
Shame on Australia though for seeming to fail one of their citizens so completely.