Part of that is the narrative, if it was Courtois or de Gea = never their fault, if it was Messi/Salad/etc it would have been tossfest over the skill.
Said it before, it's quite simple
- Keeper didn't pick the flight of the ball (people who have played competitive sport would understand this)
- Eriksen hit the ball extremely hard (saw a stat that claimed it was 84mph+), it went high (lots of stills showing how much higher than goal it was), then dipped viciously, clipping the top of bar on way in.
A hit that hard with no movement that clips the top of the bar might have beaten the keeper purely for pace, add in the movement, dip and the fact that keeper lost the flight .. it's a good hit/goal.