I just posted a response to this and now it's gone lol. Here we go again.
Daniel 9 says HE shall CONFIRM the covenant with the many. A covenant existed before HE came, his coming confirmed -(etablished the truth or correctness of) the covenant when he came.
God promised Abraham that in his seed, all the world would be blessed.... speaking of Christ. When Christ came, that CONFIRMED the promise God made to Abraham.