Saudi Arabia spent a long time getting the US to attack syria. Also Al-quaeda is/was a bigger threat, because it came from within, it started out as a jolly adventure for a low ranking Saudi Noble.
ISIS only works in a vacuum, Plus if we are going to be brutally honest, on the scale of 0 - 10 (full ISIS) Suadi Arabia is about a 6-6.9
The main difference is that ISIS show a flair for video editing of their medieval punishments. Something the Saudi state does behind closed doors.
http://www.theaustralian.com.au/news/world/cia-overseeing-su...
They, like us were arming the rebels. ISIS "formally" split from the Free Syrian Army in late 2013:
http://news.nationalpost.com/news/world/israel-middle-east/p...
When they gave up on getting us to attack them they tried a different tact:
http://www.globalresearch.ca/saudi-regime-working-to-lure-th...
In the same way that Bin Laden is a direct consequence of our actions in 80s Afghanistan. ISIS is a direct consequence of our half-arsed dicking about in Syria.