Moshiach's Principle Goal

The Rambam emphasizes, that the ultimate and complete performance of all the Mitzvahs of the Torah will be attained, when a King rules over Israel. It is then that we will fulfill the Mitzvos of: waging the wars of G‑d, destroying Amalek, and building the Beis HaMikdash.

Similarly, our observance of the Torah and its Mitzvos will be enhanced and complete. For, as the Rambam writes at the conclusion of ch. 4, "[The king's] purpose and intent is, to elevate the true faith."

This conception of the monarchy found full expression in King David, who united the entire Jewish people, completed the conquest of Eretz Yisrael, secured peace for our nation,and began the preparations for the building of the Beis HaMikdash in Jerusalem.
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Our faith and our yearning for Moshiach - as the Rambam continues, "Whoever does not believe in him, or does not await his coming..." - should therefore focus not only on his coming, but also on his restoration of the Davidic dynasty, and on the complete observance of the Torah and its Mitzvos.

With this, the Rambam emphasizes, that the conception of Moshiach's coming, and the Era of the Redemption which he will bring about, as centering around the complete observance of the Torah and its mitzvos, has its source in the Torah itself.

Indeed, it is one of the fundamental principles of the Torah, for there must ultimately be an era, in which the Torah will be observed perfectly.
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We can now understand why, the Rambam devotes a separate halachah to the designation of the three supplementary Cities of Refuge. For this indicates a further state of completeness in the observance of the Torah and its mitzvos, a state that will be reached only in the Era of the Redemption.

Not only will the Mitzvah of establishing Cities of Refuge be observed as in previous times: it will be observed in a more perfected manner, than ever before. The commandment to establish these new cities indicates, how the Torah itself points to a future era, when the observance of its Mitzvos will be complete.

Since the intent of Moshiach's coming, is to bring about a complete state of Torah observance, he need not perform miracles, since "This Torah, with its statutes and laws, is everlasting."
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When it is referred to Moshiach as "Crushing," it can be interpreted as referring to a single victory; while "breaking down" implies, that one has completely established one's authority.

Furthermore, David was victorious over "the princes of Moab," one nation; while Moshiach will rule "all of Seth's descendants," many peoples.