Imagine literally driving a large vehicle through a structure. It's about creating big, obvious disruptions. The new evidence completely drove a coach and horses through the old theory.
Pro Tip 2/3
Not Literal
It's a figure of speech, not about driving. It means to ruin or disrupt something with force. The whistleblower's report drove a coach and horses through the company's reputation.
Pro Tip 3/3
British Origins
This phrase is chiefly British English, so it might be unfamiliar in American or other varieties of English. He drove a coach and horses through convention by wearing jeans to the formal dinner.