How could Trudeau have handled his resignation in a way that would have been acceptable to you? The party leader serves an important function for the election process, and people would rightfully complain if he ran in the election with the intent to step down.

He could have privately held successor conversations behind closed doors and announced that someone else would take over for him during the election, but that wouldn't be inclusive of the opinions of Liberal voters and people would complain.

He could have immediately stepped down and called an election and the Liberals could have run without a leader. That would be unacceptable to all Liberal voters and many others and would be a stupid move.

When you have a system where the party or coalition with the most seats in Parliament elects the Prime Minister, I don't see what options you have that would satisfy bad faith arguments like yours.