Vertical scar line on belly after emergency csection. Why did they do that?

Emergency! If it was an emergency c-section then all thoughts and procedures are done to emergently deliver the baby via an incision in the abdomen. Cosmetic outcome is not a concern in those situations. Vertical incisions are the quickest way to gain access to the abdomen as opposed to the horizontal incision. Similar incisions are used for trauma cases (gunshot wound ). Glad you and the baby are ok!
Keloid? Everyone gets scars after surgery but some more than others. A keloid is a condition where thick red scars form. Injection with triamcinolone is effective. Laser treatments are also effective.