If I remember right, the reason why Mark has scholarly consensus as being written before John is that Mark is least theologically developed, which only really makes sense as evidence for that if you’re starting from the position that the theological bits are later additions. I remember Q and M as evidence for Mark before Matthew or Luke, but is there any evidence that Mark was written before John that doesn’t start with the position that more-developed theology is a later addition?
Why am I being downvoted for asking someone with a PhD in this topic a question about their expertise?