Simplify the following text for a Grade 8 native English-speaking person.
Original: After Lenin 's death on 21 January 1924 , Rykov gave up his position as Chairman of the USSR Supreme Council of National Economy and became Chairman of the Council of People 's Commissars of the USSR and , simultaneously , of the Sovnarkom of the RSFSR , on 2 February 1924 .
Simplified: After Lenin 's death on 21 January 1924 , Rykov became head of the government of both the USSR and Russia .