Getting pushed in doesn't give the attacking player the right to run over the goalie. The rules clearly say the attacking player must show a reasonable amount of effort that they at least made an attempt to avoid the goalie.
Dumoulin was closing in on Kakko. Instead of slowing down and cutting earlier than he planned, he kept going, was pushed and made no attempt to avoid contact.
Let's go through the check list
Was pushed in
Acknowledged that he may be pushed into goalie
--------Slowed down
--------Cut across before the crease
After being pushed...
--------Tried to jump out of the way
--------Give up on puck and use arms or such to minimize impact
Getting pushed while driving to the net is a given. It's always stupid for players like Dumoulin to shove players towards their goalie, but Kakko showed no sign that he cared he could be pushed or that he cared he might hit the goalie. Dumoulin also ended up slamming into his goalie, but Kakko still managing to make a play on the puck is what tipped it over as him making no attempts to avoid contact is what enabled him to do it. Any goal likely would have counted if Kakko didn't touch the puck and pass it