Muslim-ruled, not Muslim-majority
Mysore was a Wodeyar kingdom before Hyder Ali, an officer in its own army, made himself its effective ruler around 1761. He and his son Tipu Sultan governed a population that remained overwhelmingly Hindu — the distinction matters, and flattening it is the commonest error made about this state in both directions.
Tipu renamed the realm *Khudadad Sarkar*, “the God-given state”, and sought investiture from the Ottoman court in the 1780s. The claim to Islamic legitimacy was real; so was the fact that most of his subjects and many of his officers did not share his religion.
Why it is a “formerly Islamic territory”
The category is narrow and Mysore fits it precisely: land that was meaningfully Islamic by rule, and which today is no part of the Muslim world — unlike Ottoman-successor Turkey or Mughal-successor Pakistan. After 1799 the British restored the Wodeyars as a princely house, and the Muslim polity simply ended.