Confused about boyfriend behaviour

Hi everyone, I hope you’re all having a good weekend.

i had an interesting response to something I said to my boyfriend and wasn’t sure what to say or how to reply to him so I didn’t.

I work with children and a parent asked for my help with a baby harness, getting clipped up at the back. I helped as the child was already in the harness. Didn’t think any more of it.

My boyfriend got very grumpy when I mentioned I had helped with this and then said he would have left him to it and starting saying things like were was his wife. I was only just leaving work and wasn’t going to leave him to struggle.

Why would he have behaved like this? It seemed so strange and might have been nothing but I didn’t go in to detail with him about it.

Am so confused and not sure what to think.