There are millions of reasons why rich people donate items to cultural institutions.
They get a massive tax deduction which can be spread out over five years. The favourable publicity rubs off on any related pieces, which can be sold at a profit. Want to turn the proceeds of a business deal into social capital? Buy a piece of art, wait 10 years and then donate it to a public gallery.
Earlier this month the National Museum of Australia (NMA) announced it had spent $8 million on thousands of pieces of historical and decorative art "which explore Australia’s history, culture and identity" from businessman Trevor Kennedy.