My thoughts are quite simple....for many years, the Democrats have ram-rodded their agenda through both houses of Government, because despite all of their big talk, Republicans don't have the "intestinal fortitude" (a polite term for what rhymes with walls), to go toe-to-toe with the Dems. Therefore, when push has turned to shove, the 'Pubs usually buckle, and the Dems are used to this being "business as usual". This has allowed the Dems to push their "quasi-socialistic" agenda on the backs of Americans.
President Trump, thank God, isn't "business as usual", and the Dems simply don't know how to cope with it, so they're throwing a childish tantrum, assuming it will get them their way, as has been in the past. I sincerely hope that he stays the course.