Justin Kluivert hit a hat-trick and Milos Kerkez also scored in the rout.
Afterwards, Iraola told the Daily Echo: “My first feeling is very proud of my players.
“Because the performance today has been very, very good. I think we fully deserved to win today. Very complete all the minutes I would say of the game.
“And I had a slight doubt with the last minutes because you never know in a high-level game like this how we are going to finish.
“But we finished really strong also and I think it has been a very complete game.”
Iraola also said: “I think we needed this from every single player that started. And the ones who, especially Jebbo, that came at the end.
“They've played their part and a little bit extra, I would say, because they've won duels against players that are flying right now.
“We've had very good games against Newcastle this couple of seasons.
“But we talked in half that we needed really to win like this with one or two more goals. Because if it was 2-1, we've been here before and always something happens and you don't win the game.
“So we needed to continue being a threat offensively and I think we have been.”
On Kluivert's performance, Iraola said: “With Justin and with everyone. But it's true that Justin has scored three goals.
“Three very beautiful goals also. But his work rate defensively against Tonali, jumping to the press has been for us very valuable. Obviously if you add the goals is much nicer everything.
“But I cannot say just one player, two players, everyone has been very, very good.”