The Democrats invoked their filibuster privilege to block the vote to confirm Neil Gorsuch to the Supreme Court. So the Republicans used the so-called “nuclear option.” They changed the rules to eliminate the filibuster for Supreme Court nominees. The Democrats, under a previous administration, themselves went nuclear to eliminate the filibuster for other presidential nominations.
Now the Senate cannot block any presidential appointments. But the Democrats can feel good about themselves. (“Take that, Republicans! I guess we showed you, Donald Trump!”) Even though the gesture significantly weakens their power in the Senate.