I would normally be very concerned about what your husband did but in the context and if it doesn’t ever usually happen, it’s kind of understandable.
What you need to focus on is working out how to reduce your small child’s sensory overload. She clearly cannot cope with bathtime, not surprising as for a child who struggles this way, it contains all the worst elements - tiredness, water of varying temperatures, someone rubbing at their body, someone messing with their head, shampoo in the eyes, the 2 adults voices and their stress, the loud siblings, doesn’t have control, doesn’t know when it will end, contract between warm water and cold air when they get out, feel of the towel rubbing on their skin and much more. You need to put yourself in her shoes and imagine something being done to you that you can’t cope with and have no control over.
I’d sit with your husband and really have a good think about what the flashpoints are, when they happen, why they might happen and try to make a plan. The plan would include reducing sensory overload, reducing demands and building her back up to being able to relax and cope with being washed. You could accept she may be less clean than she has been and make washing less frequent. Make the process much much faster. You could build it in to a time when siblings are at clubs. You build in choices. People who are demand avoidant have a strong need for personal autonomy, so to feel she has some control might help e.g. when you’re at the shops away from the flashpoint, show her 2 cute shower gels and ask her which one she likes. Let her pick one and pay with her own coins - do lots to build positive associations with washing.
There are lots of parenting groups on Facebook. If you join e.g. parenting girls with autism (not saying this is the issue, but they are unjudgemental) they will have many great tips for situations like these.