If I took the stories and writings about St Nick / Santa Claus literally, I would expect to see a fat guy in a red suit, being pulled through the sky by flying reindeer, delivering gifts on Christmas Eve. But, as with the Bible, we know that stories get exaggerated and don't always align with what makes sense or is, in some cases, even possible.
This is the advantage that Christians have created for their beliefs. Since none of the magical events of the Bible are happening today, Christians have figured out a way to attribute pretty much any event to their God, including the creation of everything - "Things exist, so Jesus/God made them".
If a Christian gets fired from their job, it's because Jesus/God had other plans for them. If a loved one dies at an early age, Jesus/God wanted to bring them to heaven, but if someone is unexpectedly cured of stage 4 cancer, it "wasn't their time" to be taken by Jesus/God.
Basically, anything that happens, good or bad, can be attributed to Jesus/God, should a believer wish to do so.
Right. This is what I referenced above - anything that a Christian wants to attribute to Jesus/God can be proof of Jesus/God. The argument for "things exist, it must be God" only works if you already believe in a God.
Like I mentioned above, written/oral stories often get exaggerated. Maybe Saint Nick / Santa Claus is just the being that causes us to feel the spirit of Christmas and go out and buy all the gifts, not literally delivering the gifts on a slay pulled by magical reindeer.
Jesus/God have stories written about them. Saint Nick / Santa Claus have stories written about them.
There's nothing tangible, today, that proves the existence of Jesus/God or Saint Nick / Santa Claus.
The evidence seems pretty similar.