(a) It was successfully created in the lab using gain of function research they were developing
(b) It was accidentally or purposefully cultured naturally from one of the many strains they had collected from the field
(c) A researcher, assistant, or contractor was infected in the field as they were doing field work
Option (c) is particularly compelling because it doesn't require much additional complexity beyond the "official explanation". It still maintains that the origin of Covid-19 was a zoonotic spillover event, but points to the research as the direct cause of that event. And it's not necessarily the case that if the virus was in the bat population already that it necessarily would have spread. Rural populations might become briefly infected with a pandemic-level virus, but the spread is naturally quarantined since they have little contact with major metropolitan areas.