Continental's hubs were Newark, Houston, Cleveland and technically Guam for Air Micronesia.
United's Hubs were Washington Dulles, Chicago, Denver, LA and San Fran.
Cleveland was too close geographically to Chicago (and far less revenue potential) to continue as a hub. Especially after BP moved to Chicago and other corporate clients were siphoned by Delta and American with status bonuses. Continental at Cleveland tried many mini-expansions, usually using regional jets. One of their mid-west expansions one summer was pulled weeks before starting up. The now closed D concourse was all prop/regional jets and was built to only have a ten year life expectancy until the airport's 2002 master plan, including runway expansion for larger aircraft/ more trans-Atlantic routes from Continental, was completed.
There was only Cleveland-London Gatwick (moved to Heathrow after the merger in '09, discontinued with the Heathrow landing slots too valuable to keep to the Cleveland route) operating with Paris (Air France hub) and Amsterdam (KLM hub) flights were considered until post-merger Continental left Sky Team and joined United in the Star Alliance. That switched to potential Frankfurt (Lufthansa hub) route, but LH didn't have larger aircraft to spare and Continental's pre-merger 757's used trans-Atlantic to the UK, Spain and Portugal couldn't fly the distance without weight restrictions. With United's 787s in house, they could handle any of those routes. I wouldn't expect any new service out of United other than regaining some routes in the northeast or summer season to the west coast that were around until Cleveland was de-hubbed.
The Aer Lingus flight to Dublin is heavily subsidized for three years and seasonably does alright financially. It will most likely end after the subsidies run out, or cut to three times a week if it is kept operating.