Complex sentence: Shortly after the occupation, VNV decided to collaborated with the Germans and soon became the biggest party, gaining many members after disbanded in 1941 and after fusing with's Flemish wing.
Split into simpler sentences: Shortly after the occupation, VNV decided to collaborated with the Germans and soon became the biggest party. VNV also gained many members after disbanded in 1941 and after it fused with's Flemish wing.