Covered under "evil army." Point is each comic/TV show/Movie should be allowed to face those threats alone if the plot needs them to. Shared universes are fun, but "oversharing" is a drag.
Then at least they should have explained
why Jeff couldn't make contact with the others. No, it doesn't have to be done in
every case, but that doesn't mean you can treat every case as identical. Each situation is different and there can be exceptions to a general rule. In this specific case, right after
Crisis, the creators had a responsibility to show us
why it mattered that the three separate universes were now one. Particularly why
Black Lightning's still-unnamed Earth was thrown in along with Earth-1 and Earth-38. That came as a major surprise, since BL was so distinct from the other shows. So if they were going to do that, they needed to do something to justify it, to show why it was worthwhile to fold it in with the others rather than letting it retain its distinct identity. But they didn't. Aside from a couple of throwaway allusions, it had no impact whatsoever on BL's storytelling, which compels me to ask, why bother merging it? If they weren't going to
use it, they shouldn't have done it. And since they did it, they should acknowledge it in
some meaningful way. No, not in every case, but in
this one instance, as I've explained, various factors combined in such a way that some sort of reference was warranted, or at least conspicuous by its absence.