I tend to use “How come you you didn’t use x?” Or even “how come X didn’t/wouldn’t work?”, and let my body language and facial expression indicate genuine curio

I tend to use “How come you you didn’t use x?” Or even “how come X didn’t/wouldn’t work?”, and let my body language and facial expression indicate genuine curiosity,and maybe even perplexion at the scope of problem. I don’t feel Author considered the non verbal ways of communicating intent. “How come” feels slightly lest antagonistic then simple “why” but that may well be regional differences