That way they’re too busy to do all the work the other DC heroes are doing much faster.
If that’s true, what the hell could this mega crossover be planning that multiple or even a couple Supermen couldn’t face?
That is, all the Supermen will be occupied with some monumental task that requires their full attention.
If I had to guess, “Crisis On Infinite Earths” will probably employ a Superman ensemble tactic used in the comics for decades to even the playing field.