Now that Cleveland is being dismantled as a hub by United, is there another airline or airlines that would step up and increase flights. Because Delta also cut back flights at Cincinnati, is another airline going to increase service to Ohio, or would it not be feasible?
No, most of the service being cut was not economical on any aircraft.
United will still be the largest carrier in Cleveland.
Other airlines may slightly increase capacity to their hubs to capture the traffic in Cleveland that used to be able to fly nonstop but will now have to connect. However, this actually isn’t a whole lot of traffic. Many of the markets United is cutting from Cleveland did not have much local traffic.
Calling Cleveland a “hub” pre-cutbacks is a bit generous - it has about as many daily ASM on United as Guam, and is a fifth the size of the next smallest hub by daily ASM, LAX.