He "stated acting as Russia's stooge" when the Clinton people decided Russia was to blame for their 2016 elections campaign failing. Then suddenly everybody and their uncle became a Russian asset, Russian stooge, Putin puppet and so on.
Yes yes, we've heard it all before. Over 3 years of this stuff, with no evidence of any stoogery.
I don't know who is "they" but the shift in perception didn't need any prompting from anyone. It was Assange that started acting as Russia's stooge.