What evidence is there that Bach was (or was not) an earnest Christian?

That is, does the evidence suggest that he composed his Passions and
other Christian music primarily because he was a believing Christian or
primarily because it was his job (a job he did, to be sure, very, very
well)?

I hope those who know more about Bach's life than I do can shed some
light on this.

Thanks,

David Cozy <[log in to unmask]>