The suspension of the service is unrelated to the KL/AZ breakup. From what the NWA website says it was suspended by poor demand. The Rome service is apparently doing well.

It is a well known fact that the MXP airport has been having problems since it opened, and many airlines have refused to move their service from Linate or begin new service to Malpensa because of these problems. It is also a fact that one of the major reasons KLM pulled out of the alliance with Alitalia was due to problems with this airport. (The other being Alitalia's effort, or lack thereof, to privatize.)

One could argue NWA was using the capacity issue as an excuse to back it's KLM partner, but I can't imagine that Detroit could support daily DC-10 service to Milan AND Rome.

When KLM announced its intenion to end the relationship with AZ, NWA didn't seem phased by it and actually said that the KLM break wouldn't effect NWA's relationship with AZ.

Who knows?