Pre merger for many years UA maintained both ORD and CLE as hubs. The 1986 hub closure it moved the aircraft to start IAD hub. The CO UA merger killed CLE as a hub. UA picked up EWR. Remember CO can thank People Express for EWR hub.
UA had a good operation at CLE dating back to the 1960’s. Service to Florida before ORD had it.
The bottom line is the delays and cancellations at EWR and ORD are excessive especially in weather events and they was not as extreme at CLE.