Do You Have to be a Great Leader to be a Great Product Manager?

A successful product team and company turn to the Product Manager for direction so they must be good leaders. Product Management does not necessarily directly manage anyone, and most of the work is completed by influence, so by default they must be a great leader. Good leaders can succeed by direct management, great leaders cause change by influence!

In my experience, good Product Managers have to be great collaborators, a great Product Manager has to be collaborative and influential. The phrase, "expereince working in cross functional teams" and can "influence without authority" seem to be standard phrases found in a PM job descriptions. I think that it is niave to assume anyone without positional authority can get a job done as if they do, but being able to influence team members is a valuable trait of a successful Product Manager and is often needed to get things done. The degree to which influence is needed is also a vision of how well or not the company is run. In my experience, highly political companies (focus on the micro not the macro) is a great example of this. So it certainly doesn't hurt being a good leader, but it is not essential, and I've even seen it work against those in highly political environments because it threatens others.

Product Managers must be great leaders simply because one of the core responsibilities of a product manager is to identify a new product or a strategy and road map for an existing product. In either case we are talking about bringing something about that does not yet exist. As a result, unless the product manager can do this themselves, they must create a vision for the product, infect others with this vision, and then lead the team forward until the new product or is realized. 
 
There are many skills and responsibilities that do not require leadership, but if we're talking about great product managers, I don't see how a great product manager could be successful without strong leadership skills.