John McCallum did not resign, he was fired by Trudeau for being caught doing Trudeau's bidding.
For Trudeau and the Liberals, it is all about winning this upcoming election and turning Asian-Ontario swing ridings to the Liberals and retaining existing Asian-dominated Liberal ridings.
That is why McCallum gave a 40-minute speech to only local Chinese-speaking newspapers in the Asian-dominated town of Markham about why McCallum and the Trudeau Liberals thought Meng Wanzhou, the Huawei CFO had a strong legal case against America's extradition request for her to be removed to the U.S.