One could blame poor refereeing. Or a lack of effort. Or that the Seattle Sounders played without passion. That would be passing off the blame. It wasn't in Seattle's head, or referee Mark Geiger's. Seattle was out played. Poor passing out from the backline compounded by poor passing in the middle. That wasn't the only place were Seattle played poorly.
Every Montreal Impact goal came due to poor defensive play. Not from just one player. When a Zach Scott, or Marc Burch or Brad Evans (at fullback) misplayed the initial dribble the centerbacks didn't close down the shooting angle. Poor control of the central midfield (no Alonso) led to quick balls to the flanks. Those flank players were given space to create and slotted goals home. Patrice Bernier played great balls and earned his assists, but much of the credit belongs to Felipe Martins, Justin Mapp and Andrew Wenger.
By the time former Sounder Lamar Neagle scored the fourth the game was well out of hand. Whether Geiger's ruling of a Jhon Kennedy Hurtado red card is overturned or not will not matter. Seattle was the worse team.
Eddie Johnson did well with a chippy shot after a brilliant Fredy Montero throughball. His errors, no matter how harsh you can rate him, were not the difference. The forward pairing isn't immune from criticism, but their chances were so few that focusing on their failures would be a mistake.
Montreal deserved the win. Maybe not 4-1, but they were the better team on the evening. Their passing was better. Their defense more organized. Their keeper didn't misplay balls he could stop. Seattle's defense is in the process of regression, they aren't this bad. But they clearly aren't as good as their goals against average make it seem.