It was all about Paul and how he survived the snake bite showing he was of G-d. Then many years later that snake handling verse(s) was added. So it’s all about how Paul survived that instance in his ministry.
That’s what I think, too, but I’m not going to say that section absolutely wasn’t in the original Mark. It makes Mark a bit later date (59-60 AD) than thought since the snake bite was on Paul’s journey for trial in Rome, about 59 AD.