Question: Why would the Romans torture & kill 10's if not 100's of thousands of people who chose to belong to an ideology that they themselves "engineered"?
ok... you are talking about what I would essentially consider a myth.
Just like most all of the "Jesus" story and everything associated with it, it was written later on to give substance to "fake news".
For instance, Tacitus a Roman Historian who wrote about the persecutions of the early “Christians”...these writings supporting the persecution were mysteriously found in the 15th century in the forests of Germany, following a reward offered by Leo X for old writings, and following a history of forgeries in Catholicism.
There are actually a lot of other references we could talk about for days on here to the myth of Christian persecution as you describe it. You are also assuming early Christian cults pre-Constantine are what we consider "Christian" today, what a very JW thing to think lol.
Whatever Christians were before Constantine, there was likely no great state-sponsored persecution as you claim, and the form that Christianity took post-Constantine (today as we know it), was an exercise in propaganda for political reasons.
can you imagine, someone lying for political reasons and making up stories???