Boeing did all they could to get the US govt to prevent that sale from happening.

If I remember correctly, when the sale was completed, it was a common opinion that Boeing’s tactics had completely backfired.

Let's just say it was a classic case of foot shot by Boeing.

They absolutely wanted to kill Bombardier, but due to the fact that Airbus stepped in, took over a majority of the project and assembles the plane in the US Boeing's calculation badly backfired.

Because the only thing Boeing fears more than one viable competitor is more than one viable competitors.

The alternative is developing a new aircraft type to beat the competition, which Boeing will avoid if it can due to this massive risk and cost involved; they only have to look at the fate of bombardier for a cautionary tale.