Radak: This was so others will not realize. (It seems that this applies more to the other opinion - refer to 1:25:1:2! - PF)
2)
Who struck the city?
1.
Malbim: The Shomerim themselves.
1
[The Shevet] should have seen that Hashem is with them - but even so, they did not dispossess all the places listed below.