Apparently the senate was set on voting against the act, which is very uncommon considering that they usually rubber stamp whatever the MPs voted for. That's not the official reason but it's the only one that makes sense considering the timing.

I guess the senate reforms to make it more independent actually yielded some results (one of the good things trudeau did, back when he was a lot less politically hawkish). The lawsuits were also piling up but those will continue I think. In any case this has been a disaster for the liberals and for Canada's reputation and I'm pleasantly surprised by the senate. I can see why it's not necessarily an uncessary, antiquated institution now. Checks and balances!