S1:N0: starts a drop database.
S1:N0: drops all sharded collections.
S1:N0: runs dropDB on all shards + clears the db metadata in all nodes.
S1:N0: steps down but managed to send the command to remove the authoritative data to the CSRS.
S1:N1: Steps up.
S1:N1: Some operation recovers the metadata associated to the db being dropped.
CSRS: Removes the db entry from config.databases.
S1:N1: Resumes the execution of the dropDatabase.
S1:N1: No information associated to that dbName is present on the CSRS, so we jump to the second phase of the coordinator, in which we send a flushRoutingTable to all nodes but the primary.
S1:N1: Completes the execution of the dropDatabase but the primary node still believes it is the primary shard for that db name.