It actually is, for a systems failure as large as the 2008 collapse, there is very rarely any one single cause.
Which is not to say that it had anything to do with OPEC or high oil prices either. If anything high oil prices should have prevented or slowed the bubble from growing.
The deregulation may have increased the scale of the problems when the bubble burst, but it wasn't the root cause of the bubble. The bubble was global, so it couldn't have been deregulation in the US that caused it.
The root cause of the bubble was mostly the unprecedented stretch of low interest rates that was also responsible for the dot-com bubble. One bubble burst, but the source of the loose money remains, so it just inflates a new bubble somewhere else. You simultaneously had the US and European central banks running a loose monetary policy while there was a giant savings glut in Asia.