Those angels who 'kept not their their first estate' were those angels from Genesis 6 who mated with human women.
They were not all of the Fallen Angels, but only those who mated with the human women (Gen.6:1-4 cf Ps.82:6-7) and were drowned in the flood and placed in 'everlasting chains under darkness' (Jude 6)
See Clarance Larkin, 'The Spirit World'
You're reeeeeeeally embarrassing most of those on the premill side of the debate with such an *explanation*.
THAT is a riot!!! Do you watch a lot of TBN??? LOL
Flatly contradicted by Scripture....
29 Jesus answered and said unto them, Ye do err, not knowing the scriptures, nor the power of God. 30 For in the resurrection they neither marry, nor are given in marriage, but are as the angels of God in heaven.
Normally, I don't like the RSV, but their rendering of v. 29 drives the point home in plain English -- "You are wrong!!!"
(Jude24 washes himself off for quoting the RSV....)