Why did Allah Almighty not create all people as Muslims, and why does He create disbelievers when He knows they will be so?

The etiquette of servitude to Allah Almighty must be emphasized, for He does what He wills and is not questioned about what He does. Allah created humanity with an innate disposition (fitra) for His oneness (Tawhid (definition)) and worship, but human and jinn devils led them astray from their religion and called them to polytheism, as stated in His Almighty saying: "And [mention] when your Lord took from the children of Adam - from their loins - their descendants and made them testify concerning themselves, [saying to them], 'Am I not your Lord?' They said, 'Yes, we have testified.'" [Al-A'raf:172]. And in the Hadith (definition) Qudsi: "Indeed, I created all My servants as monotheists, but the devils came to them and led them astray from their religion." When people deviated from monotheism, Allah sent messengers as bearers of good tidings and warners. Some obeyed, while others followed Satan. Allah Almighty said: "Mankind was [of] one religion [then differed]; so Allah sent the prophets as bringers of good tidings and warners." [Al-Baqarah:213].