Countries pursue war to advance their interests. Iran funds proxies and political parties abroad to be able to maintain sufficient influence on its neighbours to prevent the advancement of US interests and to prevent them from attacking Iran, as well as to destabilize some gulf states.

Democracies are just as warmongering as any other. The US and most European countries didn't see any issue in bombing Syria and Libya back to slavery, so why do you think democratic Iran will be any better?

Simple reason - constant war mongering isn't something politicians will be supported for because the price for that is going on the people. That is, if politicians have to answer to anyone (thus democracy).

Dictatorships on the other hand don't care about squeezing their own populations to the bone for their war mongering. Well, until the point there is an uprising of course and they are burned down by the angry mob.