You're correct; there is no History of the Church by Eusebius in the Bible. But events did occur after the Ascension of Christ. Did all progress of mankind stop once the 73 books of the Bible were written? Was this the end of all recorded history once the Scriptures were written (the last of which was written around 90 AD.)? [Don't tell me, if God meant for man to fly we'd be born with wings.] The destruction of Jerusalem isn't discussed. Did it never happen? Nor is Hannibal mentioned in the Bible; did he never invade Rome? Nor is Hitler mentioned in the Bible; did he not kill 4 to 6 million Jews and Christians?
Eusebius recorded historical events as they related to the Church. Those events show that the Kingdom of God on earth (the Catholic Church) had a functioning hierarchy with Peter at its head. In short it existed; it existed from the ascension to at least Eusebius' time. Eusebius' history records some events surrounding the original 12 Apostles, mentions many of the written documents of that early Catholic Church, including what we know as the Bible today. So, whether or not Eusebius was right handed or not, whether he was an appointee of Constantine or not, we know that;
during the reign of Claudius, the all-good and gracious Providence, which watches over all things, led
Peter, that strongest and greatest of the apostles, and the one who on account of his virtue was the speaker for all the others, to Rome against this great corrupter of life. He like a noble commander of God, clad in divine armor
proclaiming the light itself, and the word which brings salvation to souls, and preaching the kingdom of heaven.
Church History (Eusebius) 2.14.6
Thus there was an organization, it was headed by Peter commanded in divine armor spreading the light of God's Word of salvation.
Now let me ask a question. Where did your faith come from: from the Bible? And how did the Bible come to you through some 2,000 years of this so called non-biblical history? Who decided which of the Holy Scripture was to be included?
JoeT