So Constantine was able to accomplish in a few years what his predecessors could not in 300 years! And he did this under the cover of a Edict of Toleration. Sorry but there is no evidence of such a persecution. You cannot just make up history to fit your preconceived ideas.
There is massive evidence of persecution, that has been openly discussed for the last 300 years, and was the reason that catholicism was considered criminal at the founding of this country.