It always was pro-Russian. I think they feel a bit bombed out right now. Wouldn't you?

The steelworks troglodytes are just a side show, of no material relevance.
The city is heavily damaged, a new council administration has been appointed, it has been accepted into the Donetsk republic, and reconstruction is already commencing.
The so called but ex-mayor and his cronies fled to Kiev back in February. He's like President Guiado of Venezuela- a meaningless babbler. But they need the laughs in Mariupol.
^ Not by any chance selective media pickle? I mean this war is being totally objectively reported by the western press, surely? Free media, right?
Agreed- Russian speaking does not necessarily mean pro-Russian. Many non-Russians in Ukraine still speak Russian as their lingua franca, and not all ethnic Russians want to be part of Russia anyway. Given it's population decline, not all Ukrainians want to be part Ukraine either.