You said it was the root cause and the invasion empowered radical Islam. How? The failures of Maliki and Obama led to the vacuum, not the invasion that smashed Saddam and had stabilized Iraq until Obama goofed it up with his indifference.
No, invading Iraq led to the vacuum and George Bush signed the status of forces agreement that stipulated that all US combat forces would be out of Iraq by December 31, 2011. That was the agreement.
not the invasion that smashed Saddam and had stabilized Iraq
If Iraq was so stable, leaving shouldn't have been an issue.