According to "Chernobyl" writer producer in the associated official podcast, Legasov was not actually present at the final court scene in the final episode. The trial was "inspired by factual circumstances" and "compressed".
This is a poem of Konstantin Simonov written about the loss brought by the war (WWII). The peom is named Smolenschina. You can find the translation on the web-site 'Simonov through English Eyes'.
In April 1986, the city of Chernobyl in the Soviet Union suffers one of the worst nuclear disasters in the history of mankind. Consequently, many heroes put their lives on the line in the following days, weeks and months.