I don't think there is just one answer.
Some of Them want to destroy it by shrinking down to a much smaller (and with many fewer people) - but fully controlled - civilization; dedicated very completely to the service of its leaders' gratification. This will never happen - for many reasons - but is a strong motivator for 'the billionaire class' who have proximate control of things at present.
Some of Them want to destroy civilization because there is still considerable Good in it. They focus their vast power and influence for destruction at anything old, traditional, beautiful, true or moral; and at marriage and the family - as the deepest and most motivating human sources of potential Good.
Some of Them - especially the actual demons, rather than the demon-serving humans - want to destroy civilization because They want to destroy everything: all that is created. And by destroying civilization they will unleash mass starvation, violence and (real) plague. Demons greatly enjoy this, and being disembodied spirits, do not themselves suffer.
But why now - given that there has been potential to destroy civilization for several generations at least?
The answer is simple - before civilization was destroyed the powers of purposive evil needed to win over the mass of mankind to their side.
They needed people to want to destroy civilization for this to have the soul-damning outcomes they desire.
If civilization had been destroyed before Satan has won over the mass of Mankind; then increased this-worldly suffering would (probably) have led to mass conversions to Christianity.
In the past, as civilization and its worldly possibilities collapsed, this would potentially have led to an increased concern with the reality of the world to come; and the possibility of resurrection into Heaven would have become more and more appealing.
Therefore, mass apostasy, and the triumph of de-spiritualized materialism, atheism, the inversion of values; and the desire for biological death to be annihilation - needed to be in-place before the end was unleashed.
So that is why the end of civilization is happening now.