الْيَوْمَ أَكْمَلْتُ لَكُمْ دِينَكُمْ وَأَتْمَمْتُ عَلَيْكُمْ نِعْمَتِي وَرَضِيتُ لَكُمُ الْإِسْلاَمَ
This Day, I have perfected your law for you, completed My favor upon you, and chosen for you Submission (Al-Islam) as the System of Life.
What was the reason that foreced Hadith collectors to challange this statment of Qur'an and making their collections as part of Islam ? In my humble opinion these Hadith collectors tried to confound the central aims of the message, as mentioned by Qur'an
22:52 Yet whenever We sent a Messenger or Prophet before you, Satan (satanic people) tried to confound the central aims of the message. But God, renders null and void all the aspirations Satan had. And God makes His messages clear in and by themselves. God is All Knower, Wise.
[Satanic people then tried to alter his teachings after he passed on. God sent another Messenger to restore the purity of His messages. Then, God revealed His Final message and Himself guaranteed its accuracy and preservation. 5:48, 6:113-116, 15:9, 16:101, 22:52]
22:53 (God allows) these satanic people to advance their aspirations so that He might make this conspiracy a test for people and distinguish (the true believers in the Divine revelation) from those who have a disease in their hearts and who are hardened of heart. Surely, those who relegate the Divine revelation in favor of human aspirations create great schism and sectarianism. [Zulm = Displacing something from its rightful place = Oppression = Violation of human rights = Relegation of the truth = Wrongdoing. 2:53]
22:54 Those who have been given knowledge, will recognize that this (Qur’an) is the truth from your Lord, and so they accept it. Then their hearts are made humble to it. God Himself is the Guide of those who choose to believe, to a straight way. [5:48, 15:19]
22:55 And those who reject faith will not cease to remain in suspense until the Hour suddenly comes upon them, or there comes to them the suffering of a barren day (devoid of all hope).