Bridging their minds was a mistake on the villain’s behalf, because their yin and yang connection and shear force strength formed a dyad. If their minds weren’t bridged, and the connection wasn’t made, a dyad wouldn’t have happened. That’s how we have both these things together in the trilogy.
This is the canon answer, from a certain point of view.
As Chris Terrio said, it’s up to us to figure out when the dyad truly started (which is extremely lazy btw). He said that the mind bridging either was what started it, or the dyad started before that and the mind bridging only accelerated it.