Why does Jeff Bezos keep buying launches from Elon Musk?

Over the past five years, a unique set of circumstances has caused the Falcon 9 rocket to be just about the only Western rocket with any spare capacity for launching mass into orbit.

The Russian invasion of Ukraine, and resulting sanctions, took the Proton and Soyuz vehicles off the market for Western satellite companies. SpaceX's main competitor in the United States, United Launch Alliance, has been going through a protracted process of developing the Vulcan rocket, and these delays have slowed the company's flight rate to a trickle. Similarly, both Japan and Europe have been modernizing their launch fleets, and the H3 and Ariane 6 rockets are only getting going now. Finally, at Bezos' Blue Origin launch company, development of the large New Glenn rocket has been slow as well.