I just want to point out that the reason they might have texted so late could have been because, as a PP said, it took that long to unpack what was wrong.
This is exactly how my mum found out I was being bullied when I was five.
On Sunday night I told her I was sick and didn't want to go to school. It took hours of her coaxing me to admit I didn't want to go because a boy in my class was being vile to me. I'm not saying your daughter is anything like as horrid as my bully was.
But the school were completely unaware of it even though it had been going on ages. I was too ashamed to tell anyone.
It's likely the one mother then spoke to her friend somewhat upset on discovering her daughter had been hurt and then the other mother revealed her kid also had a bad experience with your child that week.
So while the approach of these mothers may seem overly hasty to you and others here, i imagine they did think they were giving you a kind of warning to talk To your daughter in the morning.
I'm sorry for you OP because it's hard to unravel what happened. But you husband's attitude is the least helpful here. I would take it seriously. It's not the school's responsibility to correct your children. No parent is always there on the sidelines to correct bad behaviour, the point is children are supposed to learn and remember how to behave.
Your daughter is very young and I really doubt she's a bully. But I just wanted to provide some context for how I could see this all coming about.