William fitzosbern and bishop odo of bayeux (williams half brother and childhood friend)
Harold godwinsons mother gytha
Dealing with affairs there and staging a triumphal tour of taking his prisoners (edgar, edwin and morcar) of the country
Absence in leadership
Due to the northern rebellion and partly because of the taxation system
The fact that william came back from normandy shows it was a serious threat because he didn't come back for other rebellions and left odo and william fitzosbern to deal with those.