The fact that he was in Sweden already? And the fact that he fled to the UK, the closest ally of the US in Europe as well as a NATO country, unlike Sweden? And perhaps the fact that he now plans to seek asylum in France, another NATO country?

It's very convenient how this conspiracy theory of the US snatching Assange from Sweden cropped up just as he was accused of a crime in Sweden I would say.

None of this requires a conspiracy theory or 'snatching'. Assange is scared of being arrested, and once he is in custody, being extradited to the US somehow. The Sweden/UK details are irrelevant.

The conspiracy theory is the one that he will be extradited to the US on "secret charges" as soon as he is arrested in Sweden. Some others in this thread compared it to other CIA grabs, for example one in Italy.