He's extremely willing to cave to the right and will run a centrist campaign to appeal to them while ignoring the success of someone like Mamdani who gets broad support for having a spine

Newsom has a history of using transphobic language and stances, has removed funding from LGBTQ+ organizations in California, has been spearheading the destruction of homeless camps without any alternatives for the people impacted, came out in support of Israel "defending itself", and has hosted multiple right wing christo-nationalists on his podcast. When kirk was killed, he immediately posted in support of him and his family and said nothing about a school shooting that occurred on the same day. A few months ago on bluesky he casually posted about how after Trump deployed armed forces to CA, he's since been using the NG himself to do drug interdiction operations within the state.

Gavin Newsom is an opportunist, simple as. He does not care about the working class or stopping fascism, just making sure he gets ahead himself. His interns might be memeing on Trump on Twitter to appease his base, but he's been pushing moderate and right wing policies increasingly in response to the Trump regime gaining traction. He sees the writing on the wall and wants to position himself for upcoming elections as a good option for disenfranchised right wingers and centrists, and doesn't care if he throws people on the left under the bus to do it.

Edit: Just to get ahead of the inevitable, I am a leftist who voted for Harris, and would vote for Newsom if forced to by the DNC. Not because I think either of them deserve any ounce of power over this nation, but solely because FPTP voting fucks over voters and forces people like me to pick the "not outwardly fascist" option. Our best course of action is to support progressive candidates so we won't have corporate center right posers forced on us in the first place.