What is the explanation of blessing only being found in a thing hidden from the eye?

Toras Chaim: It is not discussing the idea of Ayin Hara, as the Gemara then continues to discuss a person who comes to measure his produce in his granary and certainly a person does not create Ayin Hara against himself. Rather, it is teaching that it is only respectable for a miracle to come in a hidden way.

Kli Yakar: It is an allusion that success in this world is not the ultimate blessing as everything in this world has a limited measure and quantity and is transient. The ultimate blessing is the eternal reward in the next world which has never been seen by the human eye.

Maharal: The eye defines limits on every item, but blessing is unlimited.

Iyei haYam: Unlike the Maharsha who writes that 'Davar haSamui Min HaAyin' and 'Ein ha'Ein Sholetes Bo' are the same thing, we could suggest that they are different. 'Davar haSamui' refers to the owner's own eye. Once he has measured his own produce, blessing cannot rest. On the other hand, 'Ein ha'Ayin Sholetes Bo' refers to others seeing it and giving it Ayin Hara.