Why did he celebrate that way?

Chelsea defeated Arsenal in the Europa cup finals by 4:1. The opening goal for scored by the former arsenals and now Chelseas striker Oliver Giroud. He celebrated and later said that it was never his intention to do so. He said:
“It was a good final and we have been better, more efficient in the second half.
“I am very proud, this team deserved to win something. It was special for me, I am happy for this club. It’s my second trophy in two years.
“These two clubs changed my life, they gave me the opportunity to play in the Premier League.
“I didn’t want to celebrate against Arsenal but I am so proud to win this trophy with Chelsea.
“When you give me the chance to get game time I always try my best. It was our second target to win the Europa League after finishing in the top four so I feel blessed.”