We already have an explanation : it is infused with "strange netherese magic" that puts it in stasis. Classic Larian plot device, don't expect any intricacies.
From there, it likely goes to godlike power in a domination plot orchestrated by Absolute/Shar/random god.
As I said, it isn't a good explanation. It is especially poor because the tadpoles aren't really in stasis, there is a symbiotic relationship forming (e.g., tadpole powers). There is no explanation for why this might be occurring.
