This was not the offering of a pig on the altar, nor was it setting up an abominable idol in the temple area. Rather, it was an army laying siege to the holy city of Jerusalem, and thus desecrating area that the Jews considered holy.
The Romans had already been in the vicinity, but until 66-70 AD they had not threatened to tear down this relic and center of Jewish religion. So, it was in 66-70 AD that the pagan Romans violated their sacred trust by determining to completely annihilate Jewish religion, which was accomplished fully in 70 AD.
This is precisely what Daniel indicated would happen in 9.26-27, an Abomination of Desolation being set up in the holy area surrounding the "city and the sanctuary." It would result in the destruction of the same. The "people of the ruler to come" were the Romans, who in fact accomplished this deed. Jesus made reference to this very passage.
Matt 24.15 “So when you see standing in the holy place ‘the abomination that causes desolation,’ spoken of through the prophet Daniel—let the reader understand— 16 then let those who are in Judea flee to the mountains."
Dan 9.26 the Anointed One will be put to death and will have nothing. The people of the ruler who will come will destroy the city and the sanctuary.... And at the temple he will set up an abomination that causes desolation.
There are several uses of "holy place" in the OT Scriptures. Reference to THE holy place is merely a technical application of a particular holy place known to the readers, depending on context. The OT reference to "THE holy place" is always a reference to the temple room known by that name, since that was the regular application of that term under the OT religious system.
But when the language applies "the holy place" to a different context, such as we have in the Olivet Discourse, the technical application must change with the context. Instead of the room in the temple, the application is to "the city and the sanctuary" as a whole, according to its intended focus in Dan 9.26.
"The holy place," therefore, is no longer a reference to a room in the temple. Instead, the context is suggesting not a defamation of the temple and its rooms, nor a committing of idolatrous sacrilege within a holy room of the temple, but rather, a reference to its utter destruction, both buildings and religious system.
The Roman armies laid siege to the entire area, representing an unholy sacrilege in the environment of Jerusalem, with the target being the destruction of the entire set of buildings. None of this has a thing with committing sacrilege in the holy place of the temple, such as installing an idol inside of the temple. That was an earlier picture of what Antiochus 4 did, and we should not confuse the two very different AoDs!
