Fleet server y elasticsearch cluster

I have this configuration for fleet server where the servers 172.26.6.36, 172.26.6.37 and 172.26.6.38 are the Elasticsearch cluster.

172.26.6.41 is the fleet server.

Everything has been working correctly until I identified that if I turn off the 172.26.6.36 server all the agents are seen as offline.

this is my configuration

In the highlighted part I do not understand why it takes one of the 3 servers of the elasticsearch cluster, I am sure that if for some reason this one I choose is turned off I will lose visual of the agents by fleet. I don't understand what fleet has to do with elasticsearch in the configuration, do I need to choose one and in case it is not available use another one or what can you suggest me?