Major subsidiaries within a large company can and do have separate CEOs. For example, YouTube also has a separate CEO (previously Susan Wojcicki, and now Neal Mohan) under Sundar Pichai.
It’s also common within Microsoft. I can’t speak to when/why they decide to do it, but the leads for the Microsoft Gaming (Phill Spencer) and LinkedIn [acquired 2016] (Ryan Roslansky) are both CEOs in the org chart at Microsoft.
