Trust is the core of healthy relationships. They cannot function or blossom without it.
The most basic, content moments will be splintered. Anger, resentments, fears, will be condensed and boundless.
Safety is fundamental to the evolution of a relationship. Rather than the repetitive nature of the mistrust cycle. I always encourage people to have conversations or reflections on what a breach of trust looks like to them. It is a subjective definition, whereby it can look different to everyone.