According to Osho, sannyas doesn’t mechanically erase karma; it awakens you to see there were never real chains. Liberation is your nature. When remembrance dawns, the whole karmic ‘account’ is revealed as a dream and loses its hold. Sannyas is consent to be shaken awake—so the weight of accumulated karma drops, because the believer in bondage disappears.
When you truly wake up, the heavy bag of past actions is seen as pretend, so it stops weighing on you.