Any organization that designs a system (defined broadly) will produce a design whose structure is a copy of the organization's communication structure.
Melvin E. Conway

Conway's Law states that technical teams will produce code and architecture that mirrors the companies communication channels/organisation of teams.

For example, if you work in a large 200 person team, with rather disjointed communication mechanisms between all the developers, the code will look something like a huge monolith codebase with random different parts communicating in disjointed ways, with little consistency.

Conway's Law is commonly used as a justification for small teams, that can help promote a more modular, seperated codebase.