Why do Malaysia, Indonesia, and Brunei speak the same language (Malay language)
There are some similarities between the Indonesian choice of national language in 1928 as proclaimed by the Youth Pledge and that of Pakistan as articulated by Jinnah soon after the partition of India in 1947. The main logic and justification seem to be almost the same.
However, when the Malay language, renamed Bahasa Indonesia, was chosen for the Indonesian national language and Urdu for Pakistan, the process and historical contexts were very different. Linguistic controversies and conflicts exist everywhere and many people naturally, and often ideologically influenced, feel very strongly about language and linguistic identity. Each context of multilingual contacts and interactions around the world has its unique shared and different stories.
Better knowledge of multi-lingual issues faced by groups around the world and how they have tried to solve them, some succeeding while others making the situation worse, will help resolve existing and future linguistic controversies more rationally. In Indonesia, it succeed, while in Pakistan, it became a failure, although, as pointed out above, the main justifications were almost the same.