Bukayo Saka, Gabriel Martinelli and Eddie Nketiah all scored goals within 16 blistering second-half minutes as the Gunners turned the game around.
Said Benrahma had put the Hammers ahead from the spot in the 27th minute after Gabriel Magalhaes brought down Jarrod Bowen.
“Really happy with their performance first of all, and then the results,” Arteta told reporters. “And really the context of the game was that they were a goal up after a situation, a very single situation that they had attacked an open space where the referee decided to award their pen.
“Then you see the reaction of this crowd generating belief and just giving a lot of energy to the team.
“The team showed, I think, in my opinion, a lot of composure, some real quality, as well as a lot of clarity to understand what the game demanded, and they executed really well.”
Arteta reserved special praise for Nketiah, who was starting in place of the injured Gabriel Jesus.
“He is a really confident boy, but hopefully, it can give him more confidence about what he’s capable of doing, if he had any doubts,” the Spaniard said.
“I think his performance was really, really good, and on top of that, he scores a great goal. He needed it.
“Every striker needs a goal, but as well, for Eddie, and for the team, I think it is really important.”
Arteta also wouldnt be drawn into links with a transfer move for Shakhtar Donetsk’s Mykhailo Mudryk.
“You know that I never speak to other players that are not with us,” he said. “It might be that you have to ask me the question but we said that we will try to find ways to strengthen the team. We will find the right players and that’s all I can say.”