Complex sentence: During the late 1940s, he is thought to have begun expressing his opposition to strict Stalinist guidelines; at the same time, Pătrăşcanu had become suspect to the rest of the party leadership for his intellectual approach to socialism.
Split into simpler sentences: During the late 1940s, he is thought to have begun expressing his opposition to strict Stalinist guidelines. At the same time, Pătrăşcanu himself had been perceived suspicious to the rest of the party leadership because of his intellectual approach to socialism.