Complex sentence: Swimwear of the 1940s, 50s and early 60s followed the silhouette mostly from the early 1930s whereas after World War II, a new wardrobe and style of vacation-swimwear arose, coupled with an increase of leisure time and bustling postwar resorts.
Split into simpler sentences: Swimwear of the 1940s, 50s and early 60s followed the silhouette mostly from the early 1930s. After World War II, a new wardrobe of vacation-Swimwear gave a rise while the increasing of leisure time and bustling postwar resorts.