If Trudeau got involved in this case and it got leaked to the press he'd lose his job. A head of government should not interfere in court proceedings, that's extremely inappropriate.
I'm not sure how it would be some brilliant chess move for him to destroy his own career in order to appease the CCP. Canadians by and large don't blame Trudeau for what happened to the two Michaels. Either they blame China or the United States. But there's no political cost for Trudeau holding the line. Caving to China, however, would be the kind of scandal that would be extremely damaging, especially since Trudeau already has a reputation for being very friendly towards the CCP.