BIP91 is activated, why BIP141 is still dormant? The moment is BIP91 activated non-SegWit signaling blocks will be orphaned. Since BIP91 is now activated won't that immediately boost BIP9 to 100%? Why is it not happening?
BIP9 only describes a new deployment method of softforks to the Bitcoin network. I therefore assume that you mean the deployment of BIP141 by method of BIP9.

The deployment of segwit requires 95% of the blocks of a difficulty period to signal readiness for it by setting bit1 in the version field. Since the difficulty period was already in the middle when segwit got such levels of support, it can only lock in during the next difficulty period at the earliest. The next difficulty reset will happen on the ~28th (from the top of my head, you can check on bitcoinclock.org). If it has 95% support in the difficulty period it will then lock in on the next difficulty reset ~Aug 11th, and then activate another difficulty reset later on ~Aug 24th.