After Constantine is a bit tricky. During Constantine would be easier since Constantine did an incredibly amount for Christianity within the Roman Empire, turning the tables from them being a powerful minority that faced selective localised persecutions at best but otherwise was left alone into a faith that held significant controls over the levers of power and it’s own coordinated empire-wide structures that merged with state-apparatus when convenient.
Give Julian a win against the Persians and he’ll do something similar for Neoplatonic Paganism while dismantling Christian political structures to try and minimise the coordination of Christian variants with each other and diminish wider Christian control over the state.
Something which I feel alone would be enough for Christianity to remain a bunch of mutually antagonistic theologically divergent sects unable to enforce orthodoxy on each other and coordinate against a universalist neoplatonic paganism. I don’t really think Neoplatonism in this format will be able to really spread itself without state structures the same way the Islam/Christianity/Judaism could though. And its spread outside the Empire would likely be more resembling Hindu-Buddhist iconography being utilised in Maritime Southeast Asia by elites but there not being an organised religion resistant to universalist monotheistic faiths.
Which perhaps leaves an avenue for Christianity to both spread and reconfigure with the institutions needed to develop and gain control of a state to further spread around the world. Though it’d have much more competition due to the setbacks experienced in this timeline. Though resistance towards its spread within Rome could make the wealthy and still powerful Christian groups to expand abroad earlier in directed pushes.
Give Julian a win against the Persians and he’ll do something similar for Neoplatonic Paganism while dismantling Christian political structures to try and minimise the coordination of Christian variants with each other and diminish wider Christian control over the state.
Something which I feel alone would be enough for Christianity to remain a bunch of mutually antagonistic theologically divergent sects unable to enforce orthodoxy on each other and coordinate against a universalist neoplatonic paganism. I don’t really think Neoplatonism in this format will be able to really spread itself without state structures the same way the Islam/Christianity/Judaism could though. And its spread outside the Empire would likely be more resembling Hindu-Buddhist iconography being utilised in Maritime Southeast Asia by elites but there not being an organised religion resistant to universalist monotheistic faiths.
Which perhaps leaves an avenue for Christianity to both spread and reconfigure with the institutions needed to develop and gain control of a state to further spread around the world. Though it’d have much more competition due to the setbacks experienced in this timeline. Though resistance towards its spread within Rome could make the wealthy and still powerful Christian groups to expand abroad earlier in directed pushes.