Here is a good piece on the necessity of the historicity of Biblical truth: History, Reality and the Resurrection.
Among other things, the Gospel is historical. A Gospel independent of history is simply a contradiction in terms. It is no Gospel. Biblical faith and history are inextricably linked together. The Christ of faith is also the Jesus of history.
“13 if there is no resurrection of the dead, not even Christ has been raised; 14 if Christ has not been raised, then our preaching is vain, your faith also is vain. 15 Moreover we are even found to be false witnesses of God, because we testified against God that He raised Christ, whom He did not raise, if in fact the dead are not raised. 16 For if the dead are not raised, not even Christ has been raised; 17 and if Christ has not been raised, your faith is worthless; you are still in your sins. 18 Then those also who have fallen asleep in Christ have perished. 19 If we have hoped in Christ in this life only, we are of all men most to be pitied. 20 But now Christ has been raised from the dead, the first fruits of those who are asleep.” (1 Cor. 15:13-20)