You're wrong my friend. The KSA have been slapping Iran for long and the latter never dared to take it's revenge on it's own, they only arm and train terrorists here or there. Let's get back a couple of years:
1- The KSA was the main financier of Qadisya 2 war, and Iran couldn't do anything about it except moaning.
2- In 1986 two Iranian jets were shot down and Iran couldn't do a damn thing about it.
3- In 1988, 400 Iranian terrorists were killed after they tried to ruin Haj, and yet Iran couldn't do anything except moaning.
4- After 1988, Iranians were banned from Haj for two years until they abode by strict Saudi rules, and again, Iran couldn't do anything about it except submitting to Saudis.
5- In 2009, Saudis crushed Houthi terrorists and again again, Iran did nothing other than yelling and crying.
6- In 2011, the KSA and other GCC played a decisive role in imposing tough sanctions on Iran, as they wouldn't have worked out without their consent to make up an shortage in oil supplies.
7- Without KSA and GCC arm, media, diplomatic and political support for Syrians, their uprising wouldn't have survived.
8- The KSA and GCC forces entered Bahrain and Iran & sellouts couldn't do anything except getting crazily mad.
BTW, regarding Huthi war in 2009, Saudis fought Taliban-like militias who are heavily armed and who as well fight from harsh terrains, but they got crushed and begged for ceasefire, while the USA have been fighting in Afghanistan for 13 years and couldn't defeat the militias.