Even if some Arab states legitimately do want the Iranian regime to collapse, they don't necessarily want it to randomly collapse right now with no clear indication of what will take it's place. Add in the fact that the major driver of this unrest, high inflation and excessive corruption, are probably not flames they want to fan domestically. Best to watch closely and cautiously keep their options open.
Ira_n_ is not Arab. They are Persian and speak an Indo-European language.
Ira_q_, is Arab. Neighbors, some of the same religion^, similar name, same-ish alphabet, similar skin tones... very different language. Arabic is semitic language, think Hebrew.
Most Muslim middle-east countries are Arab... Iran is an exception (as is Turkey who come from Central Asia, eg Turkmenistan)
Most Arab countries are predominantly Muslim. Malta is the exception, Lebanon is complicated.
^ The biggest split amongst Muslims is Sunni vs Shia (think protestants vs catholics), Saudi Arabia is Sunni, Ira_n_ is Shia, Iraq is mixed.