Influencers are typically blacklist when they are not interested in collaborating or you've decided that they are not a fit for your brand and you do not want to work with them. Once an influencer is backlisted they will no longer appear in your searches and they cannot be retrieved
Influencer can be blacklisted from within the search feature. You can either select multiple influencer and blacklist them at once or individually through their side profile.
To learn more about blacklisting an influencer, click here.