If you search for user research on Google, you will quickly stumble on UX articles, sometimes on product management articles. But in reality, everyone is doing user research: design, sales, marketing, development, etc. However, the research done by each department is rarely shared with others which creates duplicates and wastes time and money.
Let's take an example: personas. Designers are the most vocal when it comes to using them, but they are also very useful for sales and marketing. The perspective sales and marketing can offer to designers – and vice versa – will result in sharper personas.
Another example is NPS. It is usually something used by the marketing department. But the results, especially from the qualitative question (see my article on NPS accuracy for more information), can be very useful to everyone else: customer service, designers, product management, etc.
The CEO should shape a culture where user research is done collaboratively. When the company is small enough, the CEO should also be the one in charge to make sure research is done properly and is set to be useful and curated for the long-term.
After a certain size, the CEO won't have the time to do that. From there it could be the Customer Success management department for example or a dedicated research team that can be in charge. Or whatever works best for your organization.
User research should be a team sport. With everyone involved, bias is reduced, efficiency is increased, and working on research becomes more compelling. But it requires a good leader to drive the whole organization to make research useful in the long-term for everyone involved.