I’m unfamiliar with the events you’re referring to but Cap (and Namor and the original Human Torch, Jim Hammond) were almost sold to DC at one point. In 1957. Atlas, the publishing company Marvel was using at the time went under. Couple that with the Comics Code of Authority driving the sales of comics down and Marvel was almost completely done for. So much so that they had exactly one employee left in the comics division, Stan Lee, having laid off everyone else. DC, who was in a stronger position, and sensing opportunity, made them an offer for the rights to Cap, Namor and Jim. Ultimately Martin Goodman turned them down though and thus Cap remained with Marvel.