Just a guess: I think, it’s because your images are in static. Files in static are not processed by Hugo. That’s my 2 cents.
EDIT 1: Oops, my bad. Looks like, you’re already changing your static path to the content path.
EDIT 2: I can also see that you’re declaring the variable $fullPath multiple times. Are you sure that’s a correct syntax? From what I know, you can’t redeclare a variable in Hugo due to Go’s limitations and you need to use {{ .Scratch }}. See here: [solved] Unsure how to set variable value after declaring