From what I've heard, dude is super chill and that's his vibe... like he barely has a pulse. Not a confidence thing at all, although with kickers who knows.
The mental part of it is really important for them. His brother got cut by the Vikes after he missed a few vs. GB, the Raiders picked him up and he's been All-Pro or Pro Bowl level since... so he has the bloodlines and his brother to bounce things off. Bisaccia vouches for him.

Seems to me he has a big leg but he needs more time kicking in GB's conditions, and in Lambeau. My understanding is they don't let anybody practice in Lambeau so he's getting used to it.
I think of kickers like golfers - their whole process and mechanics have to be good. They all probably have good enough legs, it's about how consistent their mechanics are and how good their mental makeup is.