Constantine dressed up Christianity by putting the Emperor’s new (institutional) clothes on it. However, like Saul’s armor on young David as he prepared to fight Goliath, rigid institutionalism hasn’t been a very effective way to demonstrate the power and presence of the risen Jesus.
Prior to Constantine Christianity had been illegal in the Roman Empire for almost 300 years. Because it was illegal and often persecuted, it wasn’t able to establish a high level of institutionalism. Organizational structure and public buildings made it vulnerable to being targeted for even more intense persecution.
Constantine, however, changed all that. Not only did he legalize Christianity, but he also favored it and took active leadership in it. He called Christian leaders together from around the Empire for “church counsels” and even personally attended and oversaw some of those counsels himself. The church institutionalism that had been slowly developing over centuries in the illegal church, suddenly hardened and became rigid as the Emperor encouraged it and made it safe to develop strong organizational structure which was modeled after the Roman government with the Bishop of Rome as its head (replacing the living Jesus as the Head).
Having the Emperor’s favor politicized and compromised Christianity. It caused many people to want to convert out of political and social reasons, rather than from a desire to follow and obey the risen Jesus. Only 67 years after Constantine legalized Christianity it was made the official religion of the Roman Empire.
Some Christians resisted the Romanization of Christianity. Donatists wanted to maintain the purity of the faith and not to declare nominal (and lapsed) Christians to be a part of the assembly of believers. The Donatist were then persecuted by the institutional church until they disappeared into history.
The Monastic movement was another attempt to maintain heart-felt Christianity. Many passionate Christ-followers fled to the Egyptian desert to escape the rigidity of the Romanized church and to have the freedom to pursue a deep, personal relationship with the living Jesus. Many lived as solitaries. Some started Christianity communities that became known as monasteries.
Martin Luther set in motion a centuries-long process of fracturing and very slowly dismantling the authoritarian control of Christendom. It continues to this day and is clearing the way for Spirit-led Christianity.