These disruptions are probably costing the airlines profits and they are not in a cash flow issue. Rescheduling takes away future seats to be sold, crews and aircraft are in wrong locations cost the UA getting things back on schedule, delayed cargo has contractually penalties, shifting travelers to other carriers will have a negative impact on revenues (lost to another carrier), probably some overtime costs, .. ......

Were the airlines (not just UA, as things are worst at DL and AA presently) try to ramp up too fast and did not account for potential ATC issues, or leave enough buffer for weather or anticipate sickouts (increase COVID case), remaining supply chain issues, ... perhaps. But are they overbooking to capture cash, No. I think that is attempting to put a conspiratorial spin where none exists.

Airlines profit by increasing operations not by cancelling flights.