I was just diagnosed with an ear infection, why does this cause dizziness?

Dizziness: Inner ear infections can cause vertigo (these are usually viral and resolve over a couple of days). Middle ear infections (fluid behind the ear drum) can also cause this - these are usually bacterial. If you are diagnosed with a middle ear infection and have dizziness i would suggest you let your md know or by eval by an ENT (urgently if you have hearing loss! as well).

ear/balance canals: The balance canals (called semicircular canals) are part of the inner ear structures, so that an inflammation or infection near this area (where you have your ear infection) can cause infection/inflammation of those balance canals and make you feel dizzy. Take it easy and be cautious with walking so you don't fall. The symptoms should resolve as the infection gets better.