It is the business’ responsibility to make sure that the social media account they advertise with is properly focused on their business niche and engagement. It is also important that the content posted is engaging and interesting. Sometimes, spending more money for advertising on a more popular account will pay off in the long run.
Ask the influencer directly. Most of the major social media sites can now track post engagement. So please, ask the influencer to provide you with the details such as “website clicks”, “reach”, and “engagement”.