The entire area is a massive field of parking lots, big box stores, and empty fields. While you could concentrate more of the development along Yonge Street, you have all of this open land just available right there, why not move the subway there where it will reduce the cost of the line, better serve the people living there, and thus making it more desirable for customers (Exactly the things you complained about in your last post). The people over in Royal Orchard are being NIMBYs for the sake of NIMBYism. York University has a subway going 20m under a bunch of lecture halls and there's barely a vibration - yet somehow these NIMBYs are still worried about their house. A lot can be said about this pointless change of plans but whatever. Thankfully if Royal Orchard gets built and is now more expensive, York Region will be paying the bulk of the cost since its an ignored neighbourhood station.
I should also bring up the fact that the plan was always to bring the Subway off of Yonge Street, Option 3 just does so in a more extreme way. Even back in the 2000s when the project was first being planned, the line would follow Yonge Street until Langstaff, then curve off east until Richmond Hill Centre. The current Richmond Hill Centre Bus Terminal is directly above where the initial plans had the station located, so this whole notion you have that its under Ford that they chose to move the line off of Yonge is wrong.