Hi Andrew, this sounds like it could be a question of EAT (expertise, authority and trustworthiness) something that Google places a very high value on. In a nutshell, Google wants to rank domains that are proven to be experts in their field and they place much higher value on EAT then they do other classic SEO tactics like keyword placement.
Heres a hypothetical: If you, a large media site that focuses on a variety of topics, published an article about how a vegetarian diet is beneficial for your health that was written by a journalist and not a doctor, it would have a relatively low level of EAT. However if my smaller niche site that only focuses on health related issues and publishes content from doctors, nurses, trainers ect republished that article, it would have a higher level of EAT.
There are several ways to improve your EAT, if you have qualified people writing content about their areas of expertise you should let the world know. Tweet about them, include their names in articles and give them an "about us" or "about the author" write up on your site.
You can read your fill about EAT in the Search Quality Evaluater Guidelines if you need more details.