"take someone by surprise" is defined as "surprise someone". But then why would you use one over the other?
1a. "She bolted into the room and surprised them" vs.
1b. "She bolted into the room and took them by surprise"
2a. "The extent of the outbreak in South Korea has taken many by surprise -- mainly because the virus has not been shown to spread easily between humans" vs.
2b. "The extent of the outbreak in South Korea surprised them -- mainly because the virus has not been shown to spread easily between humans "
In other words, what is the additional effect that the phrase "take someone by surprise" has that the construction "surprise someone" lacks? I feel "take someone by surprise" sounds more official, but I might be wrong.