So Obama let it happen. Based on the history of the positions not being filled. Democrats let Trump have the right to select DeJoy.
Same story as the SCOTUS.
“On November 14, 2014 (with effect on February 1, 2015), the board appointed Megan Brennan postmaster general, to succeed Patrick R. Donahoe. In December 2014, the extended term of Mickey D. Barnett was to expire, while the Senate had still not confirmed five nominees submitted by then-president Obama.[6]”