Anyways, i just searched for russian bio lab accident and this came up first: https://arstechnica.com/science/2016/11/decades-after-deadly...
I'm sure there is more to find about that, but for the purpose of rebutting your nonsense i deem it sufficient.
What do i mean by that? The theories aren't unfounded when looking back, because they happened! It doesn't really matter where, when, by whom, and what exactly. Just that it did happen multiple times.
Cheers.
edit: Well, it even has a wikipedia article if you prefer that https://en.wikipedia.org/wiki/Sverdlovsk_anthrax_leak