Peter says that it was the Holy Spirit sent from heaven
who in fact preached the good news to these exiles. This Spirit of course is the same Spirit of Christ who spoke through the prophets of the Old Testament. We understand that the Holy Spirit used preachers to announce the good news to the exiles. Which preachers he used has not been revealed to us (though see Acts 18:23; Acts 19:10), and ultimately does not matter. That the same Spirit who laboured in the Old Testament continued to labour among the residents of Pontus, Galatia, Cappadocia, Asia, and Bithynia (1 Peter 1:1) shows continuity in the message from long ago, be it that now there is greater clarity in the glories of the message.
12 It was revealed to them that they were serving not themselves but you, in the things that have now been announced to you through those who preached the good news to you by the Holy Spirit sent from heaven, things into which angels long to look.