The presentation Jesus made in Luke 21 did not take place on the Mt. of Olives, but in the temple complex (verse 1-2). It is a parallel to the Olivet discourse of Matthew 24 (verse 3). But not the Olivet discourse.
The abomination of desolation is not mentioned in Luke 21.
“As for these things which you are looking at, the days will come in which there will not be left one stone upon another which will not be torn down.” They questioned Him, saying, “Teacher, when therefore will these things happen? And what will be the sign when these things are about to take place?” And He said, “See to it that you are not misled; for many will come in My name, saying, ‘I am He,’ and, ‘The time is near.’ Do not go after them. When you hear of wars and disturbances, do not be terrified; for these things must take place first, but the end does not follow immediately.” Then He continued by saying to them, “Nation will rise against nation and kingdom against kingdom, and there will be great earthquakes, and in various places plagues and famines; and there will be terrors and great signs from heaven. “But before all these things, they will lay their hands on you and will persecute you, delivering you to the synagogues and prisons, bringing you before kings and governors for My name’s sake. It will lead to an opportunity for your testimony. So make up your minds not to prepare beforehand to defend yourselves; for I will give you utterance and wisdom which none of your opponents will be able to resist or refute. But you will be betrayed even by parents and brothers and relatives and friends, and they will put some of you to death, and you will be hated by all because of My name. Yet not a hair of your head will perish. By your endurance you will gain your lives. “But when you see Jerusalem surrounded by armies, then recognize that her desolation is near. Then those who are in Judea must flee to the mountains, and those who are in the midst of the city must leave, and those who are in the country must not enter the city;
— Luke 21:6-21
And He said to them, “Do you not see all these things? Truly I say to you, not one stone here will be left upon another, which will not be torn down.” As He was sitting on the Mount of Olives, the disciples came to Him privately, saying, “Tell us, when will these things happen, and what will be the sign of Your coming, and of the end of the age?” And Jesus answered and said to them, “See to it that no one misleads you. For many will come in My name, saying, ‘I am the Christ,’ and will mislead many. You will be hearing of wars and rumors of wars. See that you are not frightened, for those things must take place, but that is not yet the end. For nation will rise against nation, and kingdom against kingdom, and in various places there will be famines and earthquakes. But all these things are merely the beginning of birth pangs. “Then they will deliver you to tribulation, and will kill you, and you will be hated by all nations because of My name. At that time many will fall away and will betray one another and hate one another. Many false prophets will arise and will mislead many. Because lawlessness is increased, most people’s love will grow cold. But the one who endures to the end, he will be saved. This gospel of the kingdom shall be preached in the whole world as a testimony to all the nations, and then the end will come. “Therefore when you see the abomination of desolation which was spoken of through Daniel the prophet, standing in the holy place (let the reader understand), then those who are in Judea must flee to the mountains.
— Matthew 24:2-16
You really have to be willingly ignorant to say that these are speaking of two different events.
