Russian poetry is pretty much acknowledged to be inaccessible to English readers, and there are so many Russian poets – I’m innocent of even trying to read them. Insights about Mandelstam for me are at best hearsay.
Mandelstam was born in Warsaw into the Jewish upper class, and managed to be educated in elite Russian schools as well as in Germany and France; he became known as a poet before the Revolution, and after the Revolution was alternately revered and persecuted. The fate of Jews in Soviet Russia is bitter; many tried to be loyal and fit into what is perhaps the most secular society ever devised, but the authorities under Stalin always found a flaw in their approach. Mandelstam died in exile.