Just the same way Amitabh Bachchan can be a coolie, a Shehanshah and Pa in different films.
He is a method actor (and not a spontaneous actor). He has trained himself to do what the script needs him to.
Similarly, Product management is about #ProductThinking and the ability to ask right questions. Plus, great PMs understand the food chain in any business very quickly – which matters more than domain experience.
In fact, I’d argue that domain experience sometimes is fatal for a product which needs lateral thinking / perspective.
(From my Quora answer).