They were destroyed because the “Christians” would not stand up and reclaim Rome as Christian.  Except the part where they reclaimed Rome as Christian You can't just slap a sticker on any random thing and say "this is Christian now". It has to be restructured to reflect these values. In the same way you can't slap a Christian sticker on the USSR and just kill 20 million atheists under the Christian communist regime. The USSR had to fall before the Christian Russia we see today could emerge.