Most of the early Catholic history comes from Eusebius...Much of the later Catholic history is based on what Eusebius wrote...
Supposedly many early Catholic documents are cited by Eusebius...Those documents don't exist but we are to trust that the Catholic Eusebius, Constantine's right hand man gave us the real history...
Quite often when someone is quoted from that period and one asks, 'how do you know it's true', they will have to say, 'because Eusebius said so'... And so that is what's passed of as legitimate Catholic history...Ya hafta take it for what it's worth...