Please demonstrate how this has not yet happened.
"Therefore when you see the 'abomination of desolation,' spoken of by Daniel the prophet, standing in the holy place" (whoever reads, let him understand), then let those who are in Judea flee to the mountains. Let him who is on the housetop not go down to take anything out of his house." (Matt. 24:15-17)
"So when you see the 'abomination of desolation,' spoken of by Daniel the prophet, standing where it ought not" (let the reader understand), "then let those who are in Judea flee to the mountains." (Mark 13:14)
"But when you see Jerusalem surrounded by armies, then know that its desolation is near. Then let those who are in Judea flee to the mountains, let those who are in the midst of her depart, and let not those who are in the country enter her. For these are the days of vengeance, that all things which are written may be fulfilled." (Luke 21:20-22)
The parallelism is clear. The events described happened in AD70. Allowing Scripture to interpret Scripture is the best advise for solving these apparent issues.
Show me where it did happen. It should be easy for you. It isn't the destruction of the Temple. The Abomination is something that was abhorent to God - such as the idol that Antiochus Epiphanes set up prior to New Testament times. The abomination is something that is set up - like an image of the beast.
By the way, that abomination occurs mid-point in the Tribulation period- the period which ends with the Lord's return at Armageddon. Since this has not occurred, then one must assume it is yet future.