From the Naked Bible podcast, episode 8 (Spotify, YouTube):
So how does this help us understand the passage? Briefly, baptism is not what produces salvation. It saves, in that it first involves or reflects a heart decision, a pledge of loyalty to the risen Savior. In effect, baptism in New Testament theology is a loyalty oath, a public avowal of who is on the Lord’s side in the cosmic war between good and evil. But in addition to that, it is also a visceral reminder to the defeated fallen angels. Every baptism is a reiteration of their doom, in the wake of the gospel and the kingdom of God. Early Christians understood the typology of this passage and its link back to the fallen angels of Genesis 6. Early baptism of formulas included, a renunciation of Satan and his angels for this very reason. Baptism was, and still ought to be, spiritual warfare.
Looking at Heiser’s explicit mention of “fallen angels,” this podcast may have been recorded before he proposed that demons were actually the spirits of the nephilim mentioned in Genesis 6. That demons are specifically fallen angels is Christian lore, based on some rather loose interpretations of scripture, as opposed to Second Temple writings and the traditions of the Hebrews modern scholarship has gleaned from it. To the layman, it’s not an important distinction, but Heiser’s nephilim-demon connection is a piece in a bigger puzzle that tells a different story.