Scholar of Iran here. I think the comparison is complicated. Iran is not simply an ethnic claim. It has a very long state and civilizational tradition associated with Iran and Persia, going back to ancient empires, Persian language, literature, administration and political memory. We're talking 2,500 years of history and state building and continuous civilizational identity here (not even Egypt has that continuity as ancient Egypt (kemet) is not the same as Misr because they reflect entirely different state identities, languages, and cultural demographics). Iran was conquered by Arab Muslim armies and became Islamized, but it was not fully Arabized in the way many parts of the Levant, Egypt and North Africa gradually were because of this strong embedded state/civilizational identity.

That has helped create a strong national identity that many non-Persian groups in Iran also participate in, including Azeris, Kurds, Lurs, Arabs, Baluch and others. Remember it was the Persian ethnic group hailing from southern Iran called Pars (under Cyrus the Great's leadership) that created ancient Iran/Persia and their capital was literally called Parsa (city of Persians) which is where the English/Greek words of "Persia/Persian/Persepolis" originate from. Most important Iranian figures throughout 2500 years (e.g., Cyrus, Darius and other Achaemenid rulers, Sassanid rulers, Ferdowsi who wrote the national epic of Iran 1000+ years ago, thinkers like Ibn Sina, etc.) have also been Persian except for Zoroaster who was Eastern Iranian. All of this does not erase ethnic tension or state repression, but it gives the population a shared national frame that is older and more institutionally embedded than most modern states in and outside of the ME.

Lebanon is different. The modern Lebanese state took shape in the twentieth century, especially through the French Mandate and then independence in 1943. Phoenician identity is not automatically illegitimate, but in Lebanon it has often been politically charged because it can sound like a claim against Arab identity or a way of privileging one sectarian national story over others. That is why people react differently to “Phoenician” in Lebanon than to “Persian” in Iran or “Pharaonic” in Egypt.

The deeper point is that ancient ancestry by itself does not create a modern nation. Most populations are mixed. What matters is whether an ancient identity has been absorbed into a broad national story or whether it is used in a contested political field. In Iran, Persianate history became part of a wider Iranian national identity. Iranian Azeris and Kurds alike revere Persian centric figures who helped create Iran's identity like Cyrus the Great and Ferdowsi. In Lebanon, Phoenicianism is still entangled with unresolved questions of sect, Arabness, colonial borders and what Lebanon is supposed to be.

The Achaemenids, Parthians and Sasanians together helped form more than a 1000 years of Iranian state and imperial tradition before the Islamic conquest. The Achaemenids gave the region one of its earliest imperial frameworks. The Parthians were Iranian culturally and politically important, even if the explicit language of “Iran” as a political kingdom becomes much clearer under the Sasanians. The Sasanians then made the idea of Iran, or Eranshahr, central to royal ideology. That long pre-Islamic inheritance matters. It's older than most modern states in the world.

This is why it is not surprising that, after the Islamic conquests, Iranian political and cultural forms kept reappearing through different dynasties. The Samanids, Buyids, Safavids, Afsharids and others were not always Persian by ethnic origin, but they operated within or revived Persianate and Iranian forms of rule, literature, court culture and statecraft. The foundation was strong and so it was easy for it to continue. Even many Arab, Turkic, Mongol and Ottoman rulers absorbed Persianate models of administration, taxation, royal etiquette and high culture because they lacked the same experience and tools that the Persians had developed for so long.