The early goal was the advantage that PSG had over Arsenal, coupled with Donarumma who was too good to allow any of Arsenal's ball pass through him into the goal post. Donarumma made quite some pretty saves. PSG is becoming deadly and they are not taking their matches lightly with any EPL club.
PSG had kicked out two EPL clubs out of their way in this competition. First was Liverpool and later Aston Villa. Would it be that they will still kick out Arsenal in the semifinals, the chance of that happening is very high. Arsenal needs to understand this and know that PSG is dangerous and should not underestimate them.
It is undeniable that Donnarumma's performance is quite impressive and it did not only happen in this match but since several previous Champion League matches we can see that Donarumma is really tough enough to guard PSG's goal.
Dembele's quick goal made everything look easy, throughout the match PSG players played confidently after leading 1 goal first.
This victory is quite important for PSG, it will make it easier for them in the second leg later and in terms of percentage PSG to be able to qualify for the final is very large because in the second leg PSG will play at home which allows them to win again.
Definitely, Donnarumma's consistency and crucial saves have been a key factor for PSG throughout the competition, and that early goal by Dembele gave them the momentum to control the game. PSG now has a significant advantage going into the second leg, especially with the added benefit of playing at home. The chances of them qualifying for the final seem high, but Arsenal won’t go down without a fight, and they still have a slim hope if they can play with the right intensity in Paris.