His first followers did not obtain power or riches or anything of wordly value upon deciding to follow Him.
After He died, His followers were actually ridiculed severely and had zero status in their community - especially those who maintained that they had seen the risen Lord.
In the end all of his closest followers - the Apostles - were killed - martyred - because they refused to deny the Resurrection.
And by the way, the historical facts of His life do coincide with the Old Testament prophecy - somtimes in ways that were not recognized until centuries later but now seem so obvious.
Every virtue taught by Jesus requires great selflessness - and this contradicts the world's view of power and dominion and selfishness.
His way is so counterintuitive and contrary to cultural norms - and yet people were willing to sacrifice for it and over the centuries it remains intact - despite man's tendency to abandon institutions after a half dozen centuries.
Objectively speaking there is reason not to dismiss the Gospel without further study.
Largely the same way that you know that you exist.
That's a good question. There a couple of different things I could say here, depending on what your nomenclature is for "mythology". For example, C.S. Lewis says that everyone has a mythology, but some mythology is true, and some mythology is not. For the moment I will assume that you are asking me an epistemological question about truth.
I will answer you question. But first I would like to remind you that you made a dogmatically certain assertion, first by implication, and then directly, that my beliefs are based on mythology, and I asked you how you knew that for certain. How can you be certain of that?
Now, to the 'symbols' of my faith. In the first place, every one of my opinions on these subjects is, or should be regulated by my faith in God and His Word. That having been said, my faith is not based on mere symbols. It is based on the revelation of God, both in verbal, propositional form, and also His revelation of Himself in creation, including space/time history. It is also based on the internal reality of His Presence in me.
I venture to say that the only reason you would not accept any of these evidences is your prior commitment to your autonomous self apart from God as the final judge of truth.
Now, how do you know for certain that my beliefs are based on mythology?
Cordially,