Iran doesn't control any of the Shia groups that it gives weapons to around the Middle East. The Arab world and particularly the lapdogs in the monarchies are so incredibly hostile to anything remotely Shia, that all iran needs to do is give some weapons to people who would otherwise get massacred, and then their geopolitical goals are fulfilled all the same. How that qualifies as imperialism is legitimately beyond my conception. Particularly since Iran doesn't seem to benefit in any way like a colonial overlord would expect to, nor does the Iranian economy seem to have pressing need to expand to new markets like Lenin wrote about in Imperialism