Olympia and the griffin

In 1914 a bronze griffin head was discovered in the bead of the river Kladeos at Olympia. By 1938, as Oscar Muscarella has reminded us, the griffin was no longer known in the collection at Olympia. It was purchased by Walter C. Baker in New York in 1948, and then bequeathed by him to New York's Metropolitan Museum of Art in 1971 (inv. 1972.118.54). It appears to have been part of a larger dedication that contained two further griffins, one in the National Museum in Athens (and purchased in 1869),  and the other found at Olympia in 1938 (with an ear in 1959).

How did a bronze found in 1914 (and published in 1915) end up on the New York market?

Would it be positive gesture for the Metropolitan to offer to return this significant bronze to Greece in this an Olympic year?

Bibliography
Mattusch, C. C. 1990. "A trio of griffins from Olympia." Hesperia 59: 549-60. [JSTOR]
Mertens, J. R. 1985. "Greek bronzes in the Metropolitan Museum of art." Bulletin of the Metropolitan Museum of Art 43: 20-21, no. 9 ("From Olympia"). [JSTOR]
Muscarella, O. W. 2000. The lie became great: the forgery of ancient Near Eastern cultures. Studies in the Art and Archaeology of Antiquity, vol. 1. Groningen: Styx: 22.
Picón, C. A., J. R. Mertens, E. J. Milleker, C. S. Lightfoot, and S. Hemingway. 2007. Art of the Classical world in the Metropolitan Museum of Art: Greece, Cyprus, Etruria, Rome. New York: The Metropolitan Museum of Art: 53, 415-16,  no. 36 ("From Olympia").