There is a lot of mix up and confusion between Product Manager and Product Owner . In smaller organization the two will tend to blend, for larger organization there are significant difference.
Product Managers work at the interface to development, marketing, sales, corporate strategy, controlling etc. PM works to align and balance their various perspectives. PM usually does not hold responsible for product success, their responsibility is rather for alignment and market.
Product Owners carry the actual responsibility for the product - they are making sure it really works (and pick the right features to be added, and run agile dev teams, and are accountable for the product).
Traditionally, PMs will navigate in the market while POs are accountable for the product. PMs choose the right path and POs ensure it's being taken. PMs seek alignment, POs sometimes say 'no' to actually move things ahead. Yet there is a conflict of interest: strategies chosen in PM may be short lived 'hype' and 'buzz' driven. Strategies chosen by PO may be focused on defending an existing customer base or revenue stream. In case of a dysfunctional PM-PO alignment a product strategy will not get traction in the market and growth will not happen. To overcome this, PM needs to keep the product strategy stable for a reasonable period such that it can actually be executed. Likewise, PO needs to continuously question whether the dev teams build the right features for long term product success and growth.