Poilievre had the chance to be what Canada needed (someone to actually defend it) and to capitalize on his pre-Trump momentum.
Instead as Trump took office and continuously shocked the world beyond expectations, Poilievre chose silence at first (which speaks volumes, while liberals took a strong refusal to Trump from the get go), and then some mild and unconvincing pushback on Trump, while still maintaining the Trump-inspired talking points and policies after Trump made them radioactive and dubious at best.
He has no one to thank for the loss but himself, and the Trump regime, for sending political red flags on a world scale. Stand too near to Trump in any way, become contaminated and see people pulling away from you in droves.