Matthew skips straight from the dream led wanderings of Joseph – Jesus’ step father – through the ministry of John the Baptist to the baptism in the Holy Spirit (and fire) of Jesus. And then the Father is recorded as saying, without more ado:

“This is My Beloved Son, in whom I am well pleased.”

Matthew 3:17

I think Matthew is trying to bring out the point that the well pleasing of the Son was there anyway independent of anything He had done to that point. That is the way a son ought to be to a father, well pleasing. The beloved aspect starts at birth and goes on through all their mutual lives. The well pleasing isn’t always consistently the case for any normal father son relationship. In that way this particular relationship was different.

But if there was any thing that triggered the comment from the Father that He was well pleased with Jesus, it was His submission to all the righteousness of the Spirit of God through baptism. There is something significant about obeying God that way. In this case the baptism in water was accompanied by the baptism in the Holy Spirit and both could be seen happening.

Matthew 2:19 – 3:17