In the weekday sh’moneh esrei we ask HaShem to rule over us by himself:
וּמְלֹךְ עָלֵינוּ מְהֵרָה אַתָּה י-הוה לְבַדְּךָ
and reign over us- You HaShem, alone
And yet, a few b’rachos later, we seemingly ask HaShem to give us a human king!
וְכִסֵּא דָוִד עַבְדְּךָ מְהֵרָה לְתוֹכָהּ תָּכִין.
and may you speedily establish the throne of David within it
Can someone resolve this contradiction?
The kingship of the house of David is unique in that in its most perfect form, it is merely a reflection of the kingship of Hashem,לית מגרמי כלום.
מלכות בית דוד allows us to connect, in a more tangible way to the מלכות of ה'. So essentially in both of those ברכות we are asking for the same thing: that the reality of Hashem's lone dominion over the world be made clear to all its inhabitants, and that מלכות בית דוד return, to give us a deeper understanding of that rulership and dominion.
The Drashos HaRan (drush 11) says the following:
ונמצא שמנוי השופטים היה לשפט משפטי תורה בלבד, שהם צודקים בעצמם, כמו שנאמר: ושפטו את העם משפט צדק, ומנוי המלך היה להשלים תקון הסדור המדיני, וכל מה שהיה מצטרך לצרך השעה.
So it would seem that according to the Ran the point of malchus is simply as a viable form of governing the nation due to the lack of control that would be attained governing purely by the Torah's laws. For instance, a ganav is chayev to pay double the value of the item he stole...unless he admits to the crime, in which case he only has to pay the real value of the item. If society were built purely on Torah laws, ganavim would easily be able to evade this fine of double payment which would not deter theft nearly as much. For this reason we need "extralegal" laws. The Rashba makes the same point in a teshuva (ח"ג סי' שצג) albeit not quite as elaborately as the Ran (I only included a bit of a longer drasha, you should see the whole thing, or at least the first half). Also see the Aruch Hashulchan in the very beginning of Choshen Mishpat (even before the hakdama) where he has a peice on כבוד מלך. He speaks quite a bit about how the king is the "heart" of the nation. (Perhaps one could take that peice with a grain of salt, as some say he only wrote it because of the intense censorship in Russia at the time and this was the only way he would be able to print his sefer, but I haven't looked into this).
I would add that the gemara in Avoda Zara (4a) says the following:
דבר אחר מה דגים שבים כל הגדול מחבירו בולע את חבירו אף בני אדם אלמלא מוראה של מלכות כל הגדול מחבירו בולע את חבירו והיינו דתנן רבי חנינא סגן הכהנים אומר הוי מתפלל בשלומה של מלכות שאלמלא מוראה של מלכות איש את רעהו חיים בלעו
