1)
Why did "Hashem [mi'Shamayim] El Eretz Hibit"?
1.
Rashi: He looked to see the affliction of His nation. This is like "Ki Ram Hashem v'Shafal Yir'eh" (138:6).
2.
Malbim: It was to hear the Tefilos that they pray to him at the time of Galus, i.e. "Enkas Asir" (verse 21) - he screams from his incarceration.
2)
Why does it mention "mi'Merom Kodsho" and "mi'Shamayim"?
1.
Malbim: Merom Kodsho is where His Oz (strength) dwells, above the Ma'arachah. From there He supervises and hears Tefilah. From Shamayim he released Bnei Temusah from their incarceration, via the Ma'arachah; He causes their salvation via nature, with hidden miracles.
