Adam Clarke on Acts 28:24

Some believed, etc. - His message was there treated as his Gospel is to the present day: some believe, and are converted; others continue in obstinate unbelief, and perish. Could the Jews then have credited the spiritual nature of the Messiah's kingdom, they would have found little difficulty to receive Jesus Christ as the Messiah.

Multitudes of those now called Christians can more easily credit Jesus as the Messiah than believe the spiritual nature of his kingdom. The cross is the great stumbling block: millions expect Jesus and his kingdom who cannot be persuaded that the cross is the way to the crown.