Simplify the following text for a Grade 10 native English-speaking person.
Original: Malevich 's assumption that a shifting in the attitudes of the Soviet authorities towards the modernist art movement would take place after the death of Lenin and Trotsky 's fall from power , were proven correct in a couple of years , when the Stalinist regime turned against forms of abstraction , considering them a type of `` bourgeois '' art , that could not express social realities .
Simplified: This proved correct . In a couple of years the Stalinist regime turned against forms of abstractism , considering them a type of ` bourgeois ' art which could not express social reality .