The last master of humanity, Chaldea's master, Alaya's Champion, the Pruner of Lostbelts, and a bunch of other titles were dumped on him due to his nigh-impossible feats of saving the world multiple times.

A supposedly average human with below-average skills in magecraft could become the saviour of humanity was something nobody expected.

His uncanny ability to lead no matter what and his insane charisma overshadowed his inability for magecraft.