From the memo, the purpose of these investigations is to give Democrats "access" to materials that they otherwise would not be able to see (such as Trump's income tax filings). They will then use this information to provide Democrat "views" on the issues to "castigate the majority," and draft their own "independent submissions" of questions to the Justice Department.
Furthermore, Democrats get concessions from Congressional Republicans during these investigations. They expect to hamstring Trump's use of his own office powers by poisoning the well, so to speak, to make it politically difficult for Trump to fight back. Democrats will rely on their fellow Republicans to keep Trump in check via the committees. Democrats will force Republicans to constantly call on Cabinet members to appear for hearing after hearing after hearing, making any Trump action look like retaliation.
The bottom line of their strategy is to keep the ball in play, because one never knows what may happen (other than weak Republicans capitulating under pressure). Even if it does not result in Trump's guilt of anything, Democrats still see many wins along the way.
That's why these things need to be stopped as soon as possible.
-PJ
Been thinkin’. The term civil war has been heard lately on the tube/internet. The proper response? A civil war will put Trump right up there with Lincoln as our best President ever. He will thank the left for that.