The episode highlights that they didn't "steal" money from people; they created it. This distinction is the Professor's moral shield.
By staying, he ensures the Professor’s dream survives. His sacrifice transmutes his previous cruelty into a form of dark nobility. La casa de papel 2x8
The episode concludes with a one-year time jump, providing a "happily ever after" that feels earned but fragile. The episode highlights that they didn't "steal" money