https://www.realclearpolitics.com/articles/2019/10/15/what_pelosi_really_wants_from_impeachment_141494.html
The most important thing to know about Democrats’ impeachment inquiry is this: It is not about removing President Trump now; it is about damaging him now so he can be defeated next year.
Impeachment normally seeks to remove the president (or a federal judge) from office. A successful House vote is only the first step. The Senate needs strong evidence to convict, and House leaders try to provide it with their investigation and public hearings. That’s what we learned in seventh-grade civics.
But Nancy Pelosi is not in middle school. She is teaching post-graduate courses, and she knows a Republican Senate is very unlikely to convict Donald Trump without a lot more evidence than has been brought to light along with a groundswell of public support. So, the House speaker has a more realistic goal, and it’s a purely political one. Her aim is to prevent Trump’s reelection. To do it, she has exerted tight, unilateral control over the process and handed day-to-day investigation to her California protégé, Adam Schiff, who heads the committee on intelligence. His secret hearings are in sharp contrast to the open ones held for Richard Nixon and Bill Clinton by the House Judiciary Committee.
Schiff’s closed-door sessions, his refusal to allow Republicans to call witnesses, and his prohibition of White House participation are all clear indications of Pelosi’s strategy. She and Schiff are using the investigation as publicly funded opposition research, complete with subpoena power, much like the probe that resulted in the second volume of Robert Mueller’s report.