[Alas]

As you read the commentary, you'll notice that it says "Of course as we will see later in the Book of Acts, the Lord had another in mind to replace Judas the traitor".

Stay around as we go through the book of Acts and we will come to the time that Saul is choosen.

[restornu]

Where in the Book of Acts is Saul/Paul replace Judas the traitor?

[Some hope remaining.]

You haven't shown where Matthias was rejected. It is only the opinion of some writers. Here is another opinion from the BlueLetterBible site. Go down to where it says:

Here, I must take issue with those of my colleagues who suggest that Matthias was chosen as one of the disciples in the energy of the flesh, and that it was a mistake on the part of men; that God chose Paul rather than Matthias. I believe that this account makes very clear that Matthias was chosen under the superintendency of the Holy Spirit and that he was put in the right place at the right time.

Commentary on Matthias.