This is not accurate. It is possible to say that Adorno and Horkheimer could have done more to get Benjamin into the US (Horkheimer did get Benjamin a visa at some point), but they didn't leave him to die because he was friends witch Brecht (?). I also don't really know how easy it was to get someone out of Europe during that time. Also Benjamin stayed far too long in France due to his depression and his suicide in Spain was a result of a very unfortunate miscommunication.