The Left and Islam have one major goal in common - to destroy Western Civilization whom they both view as the Great Satan. To that end, they are willing bedfellows.
Quite correct. And the both believe their vision will emerge on top. But when Islam ultimately overthrows former regimes, the bosses of the old regimes will routinely turn traitor to preserve their power.
That is why leftists tolerate Islam over Christianity. The enemy of my enemy is my friend. To a degree.
For leftists, Christianity and capitalism go hand in hand. Both must be destroyed. Leftists believe they control Islamists or live with them when the time comes....after capitalism and Christianity are no more. They are in for a rude shock.