theology - attributes of God--Why does God have to come down to check out Sodom and Gemorrah?

I've always thought it rather curious that God came down to check out the corruption of the city:

כִּי יְדַעְתִּיו, לְמַעַן אֲשֶׁר יְצַוֶּה אֶת-בָּנָיו וְאֶת-בֵּיתוֹ אַחֲרָיו, וְשָׁמְרוּ דֶּרֶךְ יְהוָה, לַעֲשׂוֹת צְדָקָה וּמִשְׁפָּט--לְמַעַן, הָבִיא יְהוָה עַל-אַבְרָהָם, אֵת אֲשֶׁר-דִּבֶּר, עָלָיו. 19 For I have known him, to the end that he may command his children and his household after him, that they may keep the way of the LORD, to do righteousness and justice; to the end that the LORD may bring upon Abraham that which He hath spoken of him.' כ וַיֹּאמֶר יְהוָה, זַעֲקַת סְדֹם וַעֲמֹרָה כִּי-רָבָּה; וְחַטָּאתָם--כִּי כָבְדָה, מְאֹד. 20 And the LORD said: 'Verily, the cry of Sodom and Gomorrah is great, and, verily, their sin is exceeding grievous. כא אֵרְדָה-נָּא וְאֶרְאֶה, הַכְּצַעֲקָתָהּ הַבָּאָה אֵלַי עָשׂוּ כָּלָה; וְאִם-לֹא, אֵדָעָה. 21 I will go down now, and see whether they have done altogether according to the cry of it, which is come unto Me; and if not, I will know.'

It seems as though what he knows, he knows from the reports given him, and comes to verify. This rather challenges the concept of God being everywhere and knowing everything.

However, I note that in earthly court something had to be established by two or three witnesses. Could it be that God sends delegates to bear witness against the city to establish His just judgement before man so man can not later accuse God?

Also God brings Abraham into his counsel on the matter, and Abraham advocates for the city in case if any righteous are present.

Similarly, I note that the angels seem to minister to God Daniel 7:10

A fiery stream issued And came forth from before Him. A thousand thousands ministered to Him; Ten thousand times ten thousand stood before Him. The court was seated, And the books were opened.

These are just really surprising personable characteristics attributed to God I don't hear talked about much.

Does your tradition address this anywhere?

Answer

I'm not sure if this answers any of the questions you ask, but I hope that it helps. Rashi's commentary on the first text you cite is

I will descend now: This teaches judges that they should not decide capital punishment cases unless they see it [i.e., they must go to the site of the crime and investigate the matter.]- [Divrei David] Everything is as I explained in the chapter dealing with the dispersion (Tan. Noah 18). Another explanation: I will descend to the end of their deeds (to fathom the results thereof). - [Be’er Mayim Chayim]).