You shouldn't exist, that's what you think.

Nahida is an Avatar of irminsul, a weakened version of Rukkhadevata. She is irminsul itself.

And somehow, Dottore managed to steal some of the branches from the irminsul, trying to create another Avatar. It worked, and you were "born"

You woke up at the same time Nahida woke up the first time. But instead of meeting the people of Sumeru, you woke up in the lab and met Fatui.