Why didn't Protestants unite with the Orthodox against Papal primacy after the Reformation?

Question

Is there some doctrinal, historical or political reason that prevented this natural alliance from taking place?
Are Protestants against the notion of the Pentarchy in general and not just against the Papacy? If so, does this mean they see the Church as corrupt already before Emperor Justinian formed the Pentarchy?

Answer 1

Because the Eastern Orthodox churches didn't want it.

For example, Martin Luther did correspond with Patriach Jeremiah II of Constantinople on the Augsburg Confession, see the Desire for Unity section of a Truth Unites 2023 video on Protestant-Orthodox Relationship: The Moment That Defined It with Martin Luther recognizing the Eastern orthodox churches as true churches (note the plural). See also Christianity Today Christian History article What did the reformers think about the Eastern Orthodox Church.

Protestants see Mainstream churches of the 3 branches as united in Christ, but they do NOT see one church having primacy over the other, hence the insistence of separate ecclesial entities. Thus Protestants are fine with the principle behind the five ancient Patriarchates seen as individual churches having equality with each other, as long as Protestant churches are also seen as equal. Protestants also maintain collegiality through recognizing baptism in those churches, and some even practice open communion. But in matters of ecclesial authority, Protestants hold sola scriptura understood as infallibility is a property of the Bible only. Although there is authority in the local church, that authority is secondary to that of the Bible. Hence all Protestants by definition reject not only the Papal infallibility, but the Catholic Church's claim to be infallible in her teaching as well.

But Eastern Orthodox churches do NOT see ecclesiology the way Protestants do. They do have collegiality and inter-communion among Eastern Orthodox churches. They do have a similar stance with the Protestants against the Catholic Papal Infallibility. But they consider Protestants heretics, although Protestants do NOT see Eastern Orthodox churches as heretics. How can there be a unity if one side sees the other as heretics?

Answer 2

Some information extracted from this article is helpful:

Pentarchy (from the Greek "five" and "to rule") is a model of Church organization formulated in the laws of Eastern Roman Emperor Justinian I (reigned 527–565) of the Roman Empire. In this model, the Christian Church is governed by the heads (patriarchs) of the five major episcopal sees of the Roman Empire: Rome, Constantinople, Alexandria, Antioch, and Jerusalem.

The Quinisext Council of 692 gave it formal recognition and ranked the sees in order of pre-eminence, but the Council and the concept of the pentarchy was rejected in the West.

The Roman Catholic Church has partially recognized the Pentarchy as an equal Pentarchy with an order of precedence starting with Rome (immediately followed by Constantinople). Oriental Orthodoxy still holds to the theory of the three Petrine sees. The Assyrian Church of the East does not recognize the pentarchy.

Protestants would never agree to submit to any Catholic patriarchal system of governance, whether Western Roman, or Eastern Orthodox (Oriental or Assyrian) because of theological differences. It has nothing to do with race.

This article explains why any form of Catholicism is incompatible with Protestantism. The fifth issue sums it up succinctly:

Soli Deo gloria emphasizes the glory of God as the goal of life. Rather than striving to please church leaders, keep a list of rules, or guard our own interests, our goal is to glorify the Lord. The idea of soli Deo gloria is found in 1 Corinthians 10:31: “So, whether you eat or drink, or whatever you do, do all to the glory of God.”

The five solas of the Protestant Reformation offered a strong corrective to the faulty practices and beliefs of the time, and they remain relevant today. We are called to focus on Scripture, accept salvation by grace through faith, magnify Christ, and live for God’s glory.

Protestants (generally speaking) see corruption spreading after the time of Emperor Constantine. What eventually developed into Roman Catholic theology had its roots in the writings of the post-Nicene fathers. While we can gain knowledge and insight by studying the early church fathers, ultimately our faith must be in the Word of God, not in the writings of early Christian leaders. Only God’s Word is the infallible guide for faith and practice.