So it was okay to investigate and jail former Presidents Park and Lee for corruption, but not okay to investigate Lee Jae-myung for arguably equal to or worse corruption:

The main opposition Democratic Party (DP) staged a large-scale rally in central Seoul on Saturday to protest against the prosecution’s widening corruption probe into its embattled leader.
Tens of thousands of party members joined the rally, as DP leader Lee Jae-myung is currently under investigation over corruption allegations surrounding a massive development project pushed for in Seongnam, south of Seoul, when he was the city’s mayor.
During the event, Lee accused prosecutors of hampering democracy by targeting him, President Yoon Suk Yeol’s former rival in the last presidential race.
“Prosecutors are taking major posts in the government, and they are threatening people with arrest warrants, instead of soldiers’ guns and swords,” Lee said during his closing remarks. “Politics is giving its place to violent ruling.”
Yonhap
You can read more at the link, but this protests shows that Lee must think he is close to being charged and headed to jail.