Obama and Rice Asked GCHQ to Spy on the Trump Campaign According to This Letter to Boris Johnson

This interesting document showed up on the 8chan qresearch general board today:

The document is a letter from GCHQ (UK's Government Communications Headquarters) director Robert Harrigan to Secretary of State Boris Johnson outlining the acceptance of a request by Barack Obama and Susan Rice to spy on the Trump campaign and incoming administration because they will "potentially compromise" "internal US intelligence".

What did the Obama administration think that the Trump campaign would do that would hurt US intelligence any more than Hillary sharing her emails on an unsecured server?