I am certain there is no emotion in the decision, and therefore not “antagonistic.” I’m also certain it’s all about money.

None of us have access to the finances of the Dl/CI code share agreement. The answer to your question could be as simple as DL not wanting to buy seat guarantees on a flight that it competes with. Whatever the specifics, I couldn’t easily find a DL flight number on the CI operated flight on a random set of February days…. is there a DL codeshare here?