Simplify the following text for a Grade 18 native English-speaking person.
Original: The period of the most significant redevelopment of the city extended from 1971 , when the Council of Ministers of the Soviet Union adopted a decision `` On the measures for further development of the city of Kishinev '' , which secured more than one billion rubles in investment from the state budget , which continued until the independence of Moldova in 1991 .
Simplified: The period of the most significant development of the city was from 1971 , when the Council of Ministers of the USSR has adopted a decision `` About the measures for further development of Kishinev city '' , that secured more than one billon rubles of investments from the state budget , until 1991 , when Moldova gained independence .