Assange is accused of sexual assault in Sweden. Sexual assault victims have the right to trial and justice, no matter who the accused is. No one is above the law, not even a famous journalist.
I think he needs to face justice in Sweden. I'm uncomfortable with the fact that the UK seems to have told the US about the arrest at the mebassy (so the US had all the extradition paperwork ready) but not Sweden.
Assange knew he would be arrested for the bail offence if he ever lost protection of the embassy. He tried, and failed, to clear that arrest warrant in 2018: https://www.bailii.org/ew/cases/Misc/2018/B3.html
The Crown Prosecution Service information for "failure to surrender" is here: https://www.cps.gov.uk/legal-guidance/bail#a32
You may want to read this article, especially the paragraph that recounts how the Swedish prosecutors were told "Don't you dare get cold feet!!" by the British chief CPS lawyer after warning that they would have to drop the charges, and how that email exchange later was deleted, contrary to protocol:
https://www.jonathan-cook.net/blog/2018-02-12/the-uks-hidden...