Inter Milan already played the final against Barcelona in the semi finals before facing PSG they didn't recover from the stress that's what I thought could have affected them in the game cause they made the final look so easy for PSG.
Chelsea against PSG in the club world cup finals is another lesson to learn but the champions League this season any team that wants to go far this season should be ready to give their all in the qualification match.
This is just another excuse you can think of to back the poor football Inter played against PSG. PSG also faced Arsenal in the semi-final what difference does it make here that they faced Barcelona which is why they were unable to win PSG in the final.
You need to come up with a better excuse as I found this one invalid. And to be honest, there isn't any excuse good enough for them to lose that game without putting up a better performance.