How have Antony's views of Brutus changed from the speech and his discussion with Brutus at Caesar's funeral? Why have they changed?

At the funeral, Antony vows vengeance against the conspirators. This appears to be done out of loyalty and true grief for Caesar. He speaks of Caesar's good qualities at the funeral to highlight the wrong that was done to him. At this point, he views all the conspirators the same. They are all motivated by greed and jealousy.

However, at the end of the play, Antony has come to the realization that Brutus is different from the other conspirators. He is compassionate and calls him "the noblest Roman of them all"(V.v.68). Antony has come to the realization that Brutus was acting out of a genuine belief that it was the right thing to do for Rome. Antony decides that Brutus will be given an honorable burial.