What's going on in his head.
Assange's behaviour is, on the face of it, getting more and more bizarre.
Let's look at the options now.
Go back to Sweden, answer questioning and potentially be prosecuted and fined a few thousand at worst. On the face of it, the logical thing to do. Fine shouldn't be an issue and frankly, most people think the law being used is really rather odd and is certainly (as far as I know), unique to Sweden. A woman being able to retrospectively withdraw consent because he refuses to take a test after an accident (condom broke) is weird. Morally, maybe he should do it, but is it really a crime? Using the term 'rape' as many people do, is certainly nothing more than smear and bigging the crime up enormously. This is the obvious thing to do and is not dangerous in any real way to Assange, so why wouldn't you do it? Even if technically guilty of the crime, you're not looking at any serious punishment and therefore trying to avoid it is massively OTT.
Second option. Assange is not just weird, but bonkers. He is either insane or has some serious mental issues. Now, interestingly, not only might this explain his behaviour, but it would also render him immune from prosecution and probably extradition. Most legal systems treat people with serious medical issues (including mental impairment) quite different to people of sound mind. This can include not prosecuting and sending them to hospital rather than prison for instance. In a case as trivial as this, with a minor fine as a penalty, non-prosecution would be the obvious route. Extradition agreements also often have a clause about the parties state of health and this can prevent extradition. If already mentally impaired, it could be argued the extradition would be dangerous to his health and this would normally stop it.
Third option. Assange is actually right and there is a conspiracy against him, he faces mortal danger etc.etc. In this option, of course Assange would flee. He's effectively trying to escape prosecution and is in essence, a refugee.
So, we know it's not option 1 as he hasn't done that. So, is it option 2 or 3? Either way, he's either right about being perscuted etc., which means we should help him, or he's certifably bonkers, in which case we should help him!! Neither option 2 or 3 would have him turn himself in and neither would suggest a prosecution is in anybodies best interests.