Many countries will think "If our biggest enemy has nukes we better get them ourself" which is one of the reasons that Iran wants nukes: To hold off Israel.
It's pretty clear that you have feelings invested in this and are picking sides which is understandable with the history of Iran and Israel but it doesn't change the facts that having nukes is most often a stabilizing event in a region (while the process up until they acquire them likely isn't) and if Iran trying to get nukes is a destabilizing event then the cause of this instability is not only that Iran wants nukes but also that others already have them and they now want them too which causes extreme tension especially in the country that already have them. This is the pattern we normally see.
>This is all before discussing how Iran and Saudi Arabia are carrying on a proxy power struggle between Russia and the United States.
Yes and again we know from history how this will likely play out. We actually have a very good example of what happens in a very unstable proxy situation when one side decides to add nuclear weapons into the mix: Korea. The armistice clearly stated No Nukes and since one side added nuclear weapons (the US broke the armistice by importing nuclear weapons into South Korea) we have seen the pariah (NK) doing exactly what Iran is doing: doing everything it can to get weapons that can stop the perceived enemy from being able to destroy them and yelling about destruction of the big enemy (which is mainly targeted at their own population).
So if history teaches us anything it is IMO that Iran will either get nuclear weapons and it will cause stability OR it will not and instability will never stop growing until full on war breaks out at which point Iran as we know it will either be destroyed or the cycle will reset.