Impeachment is quid pro quo for Nancy Pelosi. She’s second in line for the presidency via the 25th amendment:
https://en.wikipedia.org/wiki/Twenty-fifth_Amendment_to_the_United_States_Constitution
Nancy Pelosi needs to remove herself from the line of succession to the presidency or she needs to recuse herself from any involvement in the impeachment process. By the 25th Amendment, she stands to benefit from the impeachment. That’s quid pro quo.
(A) If they get Trump out, Pence becomes Prez.
(B) First thing Pence does is name a VP.
Nancy would then have to knock off Pence and the new VP.