just like Syria !?States don't like emerging hostile groups and/or governments in their backyard. They will take action just as GCC did.
Russia did that in Ukraine when NATO tried getting too close to Russia. US keeps South America strictly under its control. India keeps Nepal firmly in its grip. Pakistan reacts when India tries to penetrate in Afghanistan. Every nation does that. In case of Yemen, Iran may have pushed too far for KSA and UAE's comfort. This operation would be inevitable result. You just don't arm a group and overthrow recognized governments like that and expect neighbors to watch only.