It's not clear how the paper made these determinations, but it does assert them to be true in the second paragraph of an article on the Trump administration's plans to reduce the rights of federal employees:

"The administration describes Trump’s new rules, issued in May, as an effort to streamline a bloated bureaucracy and improve accountability within the federal workforce of 2.1 million."

While it is certainly possible that the Trump administration is motivated by a desire to make government more efficient, given its willingness to grant no-bid contracts to politically connected companies, government efficiency does not seem to be a priority for the Trump administration. A plausible alternative that the Post seems to rule out with this assertion is that Trump is attacking a group of workers that he sees as political enemies.