Luke mentions his first account, the gospel of Luke, as a record of all things Jesus began to do and teach. In his first book, Luke addresses Theophilus as “most excellent”. In the Greek it is κράτιστε, kratiste, a term belonging to or a characteristic of a high ranking dignitary or official. This word is used three other places in the new testament, all addressing Roman government officials, Acts 24:3 addressing Felix and Acts 26:25 addressing Festus.
The books of Luke and Acts were trial documents meant to defend Christianity. These documents were written to Theophilus, a Roman official whom Luke wrote to defend Christianity. Theophilus could have even paid for these documents as well.
It is a common belief that Luke’s writings were designed to defend Paul, and Christianity, against the charge that it was an illegal, anti-Roman religion. These were presented as legal documents in the defense of Paul to Cesar in Rome.
Luke always portrays Rome as the good guys. Luke was writing these documents to be presented to Cesar, so the last thing he needed to do was give fault to Rome in any way. When a riot broke out or there was some form of chaos, the blame was never cast on Rome.
The book of Luke was written as an account of the beginning of Christianity, addressed to Theophilus, “so that you might know the exact truth about the things you have been taught,” Lk 1:4; this prequel transitions seamlessly into the book of Acts; both the gospel of Luke ending and the book of Acts beginning with the ascension of Jesus.
(b)began- ἤρξατο, ērxato- to take the first step or steps in carrying out an action.
Jesus’ intentions were for us to continue what He started. Only Jesus could be the Lamb of God who could take away the sins of the world; so now that He has accomplished this, He took the first step in the redemption of man, making it possible for man to be saved by His blood; it is our duty now, by the Holy Spirit, to preach the message of the gospel of Christ and bring those in the world to salvation thru Jesus, Matt 28:19, Mk 16:15.
Jesus had much to say to the disciples, but He couldn’t because He first had to defeat sin and death on the cross and make the Holy Spirit available to all who believe, Jn 16:12. Jesus’ whole purpose for His coming was to redeem man and lay the foundation for the body of Christ, His Church; in which He is the chief cornerstone in this construction, Eph 2:20-21, 2Cor 5:17-21.