When Trump pulls out, Iran will continue to control Hormuz, and they will make sure there is no American presence in the region going forward. So, all these monarchies are going to have to deal with Iran from there on. It is entirely possible they just end up collapsing though.
The Gulf monarchies are only able to stay in power because of the US presence though. Their only chance for survival is for Trump to pull out.
When Trump pulls out, Iran will continue to control Hormuz, and they will make sure there is no American presence in the region going forward. So, all these monarchies are going to have to deal with Iran from there on. It is entirely possible they just end up collapsing though.