关于直接间接宾语和宾语补足语书上印有句子“Mary wrote an article on why the team h

关于直接间接宾语和宾语补足语
书上印有句子“Mary wrote an article on why the team had failed to win the game.”并称“why the team had failed to win the game”部分为宾语.书上又有“We showed him some photos.”为主语+谓语+间接宾语+直接宾语的例句.同时又有“I found myself in a different world.”为主语+谓语+宾语+宾语补足语的例句.
我感觉“why the team had failed to win the game”似宾语补足语多过似宾语,但那里却有个连接副词why,因而暗示这确是宾语,并且是直接宾语,前面的an article理所当然就成了间接宾语.到底我应该怎么理解?