So
for them to move to Elkhead,
Colo. to instruct the children
whose shoes were held together with string was a surprise.
请问句中的 So for them to move to Elkhead 是什么用法？
附上下文语境：
In
1916, two girls of wealthy families, best friends from Auburn, N. Y.—Dorothy
Woodruff and Rosamond Underwood—traveled to a settlement in the Rocky Mountains
to teach in a one-room schoolhouse. The girls had gone to SmithCollege.
They wore expensive clothes. So for them
to move to Elkhead, Colo. to instruct the children whose shoes
were held together with string was a surprise. Their stay in Elkhead is the
subject of Nothing Daunted: The Unexpected Education of Two Society Girls in
the West by Dorothy Wickenden, who is a magazine editor and Dorothy Woodruff’s
granddaughter.
