Head coach Clarke was axed after a fourth straight Premier League loss - a 1-0 defeat at Cardiff on 14th December - left the Baggies hovering two points above the drop zone.
Olsson, who has been at the club since 2008, has seen several managers come and go but he was still shocked by Clarke's departure after he had led the Baggies to an eighth-placed finish in the previous campaign.
In comments reported by Expressen, Olsson is quoted as saying: "I was surprised. He is a good coach who has done a lot for the club.
"We had a terrific season last season, but haven't managed to reach that level this season.
"We had Roberto Di Matteo three years ago and he was also fired. Then, we got Roy Hodgson who did well.
"The directors are hoping for something similar now."