Asalamu alaikum warahmatullah
Mustapha Kamaal Ataturk was a kaafir billah whom the whole ummah agreed to his apostasy. He was a secularist and secularism, its fundamental basis is the tabdeel of shariah and to replace it with man-constructed laws which is the very tabdeel of the shariah of Allah
we have from Imaam Muhammad Naasiruddin Al-Albaanee
Who said, in one of his earlier cassette recorded lessons, wherein he is describing an argument he had with someone about the Takfeer of Mustafah Ataturk, the secularist who converted the constitution of Turkey from the Hanafee code Sharee'ah, to the man-made laws. So Shaykh Al-Albaanee said:
"I made clear to him (i. e. his opponent) that the Muslims did not make Takfeer to Ataturk who was Muslim. No. (They did so) when he freed himself from Islaam when he implicated upon the Muslims an institution other than the institution of Islaam. And from that was the example of his equalizing between the inheritance of the male and the female. But Allaah says according to us, 'And for the male is the share of two females. ' And then he obligated upon the Turkish masses, the Qobah (i. e. a Turkish-style hat)."
– "Fataawa Ash-Shaykh al-Albaanee wa-Maqara'netihah bi'Fatawaa Al-' Ulaama", Pg. 263 from his cassette #171.]
Thus Ataturk is seen as the epitome of kufr for he is the key to the dismantling of the khilafa and from that tangent, the plight of Islam and its Muslims went down the drain, but none of this has happened by sheer luck, rather this plight is from what our own hands of brought upon ourselves that most of us always like to lie to ourselves and try to overlook. The reason why the khilafa was stripped from us because the muslims themselves stripped it from their lives, from all over the muslims world, palestinians, egyptians, morrocans, lebanese, turkish, pakistan, all over, everyone left the islamic guidance and adopted the guidance of the west, so Allah gave them what they wanted.
very few people realize or chose not to realize that the khilafa is something that is earned through Allah's pleasure, and not something that is ultimately worked for by our human efforts. that what all political groups fail to grasp may Allah guide them and us.
but as for Kamaal Ataturk, he was definitely a kaafir, may Allah put him as the leader of the munafiqeen residing lower in the hellfire than the lowest of the low.
asalamu alaikum