My speculation: having experienced the full, amazing glories of heaven and then rejecting it how could they stay?; they rejected God’s authority over them–they cast their ‘vote’ against Him; the Holy Spirit convicts of sin on earth. In heaven I assume these sinful angels had even more exposure to the Holy Spirit’s ministry and conviction of sin; the angels obviously had freedom to choose to obey God or sin. They rejected God and His best. Hell is evidence that God respects one’s free will.
” . . choose for yourselves today whom you will serve . . . but as for me and my house, we will serve the Lord” (Josh 24.15 NAS) (Jer 29.13; Jn 1.12; 16.8)