The Spain midfielder scored a stunning left-footed strike after strikes from Olivier Giroud and substitute Walcott had overhauled Mohamed Diame's opener.
And Walcott told ESPN: "He's come in to the Premier League and taken it by storm - he's our conductor.
"His goal was fantastic - I don't even know what-footed he is, to be honest!"
Wenger added: "It was an outstanding performance. If you love football, just watch him play - it's a delight to watch him."
Giroud was relieved to score his first goal since joining the Gunners from French champions Montpellier in the summer.
"I'm so happy to score my first goal and assist my friends in the team," the France striker told ESPN.
"Everyone was talking about this goal, saying 'don't worry, we trust you, keep going, concentrate'. I stayed confident."
Wenger said: "He scored at the right moment, Theo came on and scored and Santi scored a great goal.
"Theo has that in him. One or two years ago when he got in front of the keeper, he did not always finish the chance."
Reflecting on the result, which had looked in doubt after his side trailed to Diame's superb finish, Wenger said: "I am very happy.
"It was a game at a high tempo, with their first shot at goal they scored and they were dangerous in the box but in the second half we got our game going in a convincing way."
Walcott added: "It's always a tough battle here, West Ham are strong under Sam.
"It was a bit nervy in the first 15 minutes but in the second half we were much stronger.
"We know where we want to be this season, we want to be right up there at the end of the season. We showed, coming back today [Saturday], that we can definitely have a good push."