I believe UPS bought Overnite with the intent on turning it into a viable part of their business, but, they failed to foresee a few problems.
Create a "one stop shop" for all your shipping needs. IMHO they thought the LTL industry would conform to them, "UPS is here, come save us from the savages". Didn't happen, they were now a bit player in a well established industry, and they couldn't understand that.
When the little brown truck rolls up people run toward it, when the big brown truck gets there you were just next in line. That drove them ape
....
Their management style didn't translate well into LTL, strictly stops based, that was a disaster. Throwing two boxes on a porch is much different than delivering two pallets to schools, house, mall, etc. and they never comprehended that.
I could go on, but that is my opinion in a nutshell, They were in a spot they weren't used to, and when an opportunity to save face came along they took it.
They failed us, they never could adapt the UPS mentality to the LTL division and used it as a tool to sweeten the small pack pot.
They also got out of the Teamster retirement fund by offering us up to the Union.