Hello Rabbi,

This essentially means that according to Maimonides, the punishment is not a form of punishment for the sinner or purification, but rather something that aims to bring the sinner back to repentance. This somewhat sterilises the matter, because often those who sin do not also believe in the afterlife.

Alternatively, simply exterminate the sinner. Not as a punishment for him, but to get rid of him.

This is not a punishment, it is a reality.
He who does not cling to eternity does not remain.
The body decays, and so does the soul in the absence of something to nourish it.

This is not a punishment. It is a state of not achieving intelligence.
In fact, this perception comes from Aristotle, or more accurately from the interpretation of Alexander of Aphrodisias. The active intellect attains and unites with the active intellect.

The Rambam's afterlife is not a world of souls as people perceive it. In fact, it is not clear that there is a distinct afterlife for each individual, but rather the attainment in his intellect remains.
For example, if two people have the same attainment, then what remains is the same attainment.
The active intellect is only potential.

In at least one place, in the Mishnah Torah, the Rambam writes in a puzzling way the opposite. That the soul is eternal and not a potential. Apparently as a commentary by Tammuz on Aristotle.

It should be noted that according to the Rambam, keeping the commandments does not guarantee the afterlife, and it seems that even a person who does not keep the commandments can attain it (Aristotle, for example).
Nowhere does the Rambam excuse these contradictions.