And does it necessarily involve a meta-origin? Probably, but some are more controlling than others.
If the super powers are intentionally given, it could just being that the being(s) decided on this time. But then their agenda would probably dominate the setting, if only as the ever present and ever to be accounted for mystery. (Unwise to get dependent on them if the powers might be withdrawn as mysteriously as they came.) And if they had an overt purpose, there's your plot with limited variations depending on whether the characters resist or obey.
Perhaps they were accidentally triggered. The X-men were (most unscientifically) the "children of the atom" starting with Professor X's father having worked on the Manhattan Project. (Not so much emphasized after a while.) But you would need a plausible reason why the event was able to accidentally trigger them, and in sufficiently random patterns to make them superheroes rather than urban fantasy or SF. A mass magical force of randomness unleashed would probably be the most probable. 0:)
Or perhaps a magical containment spell wore off. . . was it a good spell, to contain supervillains or to give humanity a fighting chance? Or an evil one to prevent superheroes or just to make the magican unique?