However the reason why it happened relatively seamlessly in Poland has to do with the fact that after the transition the post-communists still held onto a lot of power and the most impactful branches of the government, like the secret services. This was part of a deal in Magdalenka. Poland never opened their communist archives because that would compromise many active politicians. They didn't get rid of the cancer like they did in Chechoslovakia or the DDR.
A good evidence of that was the fact that my Polish grandfather who was lt colonel of secret service (going after the Solidarity freedom fighters) still enjoyed his 10x higher pension and privileges than his victims even 10+ years after Poland became a "free" country.