The crescent isn't an Islamic symbol. The "porrai," or crescent in Tamil, of both the Emperor Shah Jahan/Mughal dynasty and of most Muslim countries today is a Pagan turkic and pagan greek influence. Turkic, because moon crescent was an important spiritual significance having symbol in Turkic Paganism of Central Asia, not in Islam. Greek, because the popularity of the crescent as an "Islamic" symbol is due to the Ottoman Turks. When invading the Byzantine/Greek Anatolia (current-day Turkey) and its major city of Constantinoples (today Istanbul), they fell on the crescent as the antique symbol of that city. As an armoury of victorious conquest, Ottomans adopted that Constantinople crescent as their own. Introducing it here and there along their Khilafat, or Sultanate, where in many areas, especially in the Near-East (Between Lebanon and Iraq), crescent was already a significant symbol dating from the Mesopotamian and other ancient civilisations times and gods. That's why Saudi Arabia and many conservative muslim states or societies don't showcase much the crescent. Instead, they use and always give proeminence to the "Shahada" or Assertion of Faith, like in the Saudi Arabia flag : 🇸🇦 . But the moon and moon crescent also have some significance and symbolism in Islam. Consciously or unconsciously, many "Islamic" historical states and their culture are, in fact, heavily relying on pre-islamic or pagan heritage, especially in the Persianate World (India is included on it). That's why in modern-day Pakistan, the traditional salutation of " Khuda Hafeez " has been transformed recently into " Allah Hafeez."