One writer comments that in Genesis 6:1–4, the reader encounters one of the most challenging passages in all of Scripture to interpret. In this article Coco seeks to challenge that thesis by pleading that a plain reading of the text is all that is required.
There are several articles available on the internet explaining who the sons of God are of whom Moses makes mention in Genesis 6. Two of these may be found here:
https://equip.sbts.edu/article/who-are-the-sons-of-god-daughters-of-man-and-nephilim
Who Are the Sons of God, Daughters of Man, and Nephilim? By Mitchell L. Chase