Very misleading article.
The "majority Sunni population" of Iraq is actually at most 20% of the population, though they had dominated Iraq since the time of the Ottoman conquest in 1534. Mosul is majority Sunni Arab, but not Iraq.
60% or so of Iraqis are Shia Arabs, with the remaining 20% Kurds, who are more or less outside the Iraqi Arab feud between Shia and Sunni.
The author here is trying to imply that the protestors are unhappy that their majority is oppressed, when what they really want is for their minority to return to its centuries-long position of oppressing the others.