The world would be a tad confused. Doesn't really line up with believing the kaaba to be sacred. Maybe people would pay more attention to those conspiracy theories that claim ISIS is a proxy for Western intelligence agencies.
Edit:
Though that wouldn't make any sense, given that Saudi Arabia is a key American ally. Maybe the consensus would just be that ISIS went off the deep in? This is a trippy one.
https://en.wikipedia.org/wiki/Grand_Mosque_seizure
Probably the closest parallel. Religious fundamentalists took over for two weeks. And Iran was having its revolution, so Khomeini took the opportunity to blame the US. Many riots in Muslim countries against the US.
Certainly useful context, but seizure and destruction are very different.
