The great tribulation is shortened for the elect's sake by removing the great multitude of the elect, saved people from Earth.  Otherwise all the elect, saved people would be dead from starving without the mark of the beast or they would be martyred for not worshipping the image of the beast.  They only go through the first 6 seals and are removed from Earth before the 7 trumpet judgments and before the 7 bowls judgments are poured out on the unsaved, unrighteous people.

Matthew 24:22, "And except those days (great tribulation) should be shortened, there should no flesh be saved: but for the elect's sake those days shall be shortened."

Mark 13:20, "And except that the Lord had shortened those days, no flesh should be saved: but for the elect's sake, whom he hath chosen, he hath shortened the days."