Illegitimate Trump

I wonder why Nancy Pelosi has not got for the jugular (in her own discreet uber-effective way). What drives Trump over the cliff every time is the L-word. His Legitimacy. I am so in awe at what Nancy has done and how she has done it that my "wonder" does not rise to the level of a concern much less a criticism. I trust her as I've never trusted a political savant previously. So, I just wonder.