This has not ever happened before. The mostly conservative media has always criticized and incited anger against the Moon administration. Why become objective all of a sudden? Sort of scary.
If President Yoon, the ruling conservative party, and most of the Korean media criticize and slander the previous Moon Jae-in administration in concert, then Korean media would likely lose credibility and seem to be under Yoon's control.
In an unusual move, Korean media has complimented the Moon administration efforts to reel in real estate loans the past few years due a booming real estate market caused by low interest rates. Recent drops in real estate prices have caused concern about foreclosures. Luckily, the criteria for real estate loans were set high enough that the drop in real estate prices will not result in foreclosures.
There was another report that stated that Yoon's policy on North Korea is the same as Moon's since they both promise economic aid in return for nuclear disarmament. Normally, the media states that Moon's administration is giving money to North Korea while South Koreans go lacking, is pro-North Korea, ignoring North Korea's human rights violations, and the like. Never a good word or comparison.
A lot of Koreans like and respect former President Moon, all the criticism is probably reflected in Yoon's low approval ratings in spite of the president's office constant daily public relations efforts.