It must be beginner's luck.

这一定是初学者的好运。

Trev: That's just beginner's luck.

崔佛：那只是初学者的运气。

His success is purely beginner's luck.

他的成功纯属新手的好运气。

Or, like many superstitions, a belief in beginner's luck might arise because of confirmation bias.

或者，和许多迷信说法同出一辙，人们会相信新手的好运是由于验证性偏差。