Getting convinced by truth is not enough

There are two phases of Faith; Ilm e Yaqeen (knowledge with certainty) and Ainul Yaqeen (Accepting with certainty)

Pharaoh was a staunch disbeliever and a ruler who imposed his Godship upon his people. They were made to believe that the Spirit of the Lord descends upon the Monarch of Egypt. It is noted in the books of hadith with a good chain of narration that once there was a drought in Egypt. The people, as his devout followers, came to him when there were no rains. They sought forgiveness for their sins and pleaded for rain. According to Baihaqi in his Sh’obul Iman, “Pharoah realized the oneness of God secretly but did not accept it. So when the people came to him praying for rain, he asked them to return the next day. That night, he went to the bank of the river and prayed to Allah, “If you don’t rain they will stop worshipping me”.  Pharoah later died as a disbeliever.

Even the relatives of the Prophets are not exempted

Abu Talib was the uncle of the Prophet ﷺ. He took our Prophet ﷺ in as he was an orphan. He loved him dearly and took great care of him in bringing him up. He always supported our Prophet ﷺ, even in his mission of spreading Islam, though he himself did not accept it.

Narrated Al-Musaiyab: When Abu Talib was on his deathbed, Allah's Messenger (peace be upon him) came to him and found Abu Jahl and Abdullah bin Abi Umaiya bin Al-Mughira there, too. He requested his dying uncle, "O uncle! Say: None has the right to be worshipped except Allah, a sentence with which I will defend you before Allah." On that Abu Jahl and 'Abdullah bin Abi Umaiya said to Abu Talib, "Will you now leave the religion of 'Abdul Muttalib?" The Prophet ﷺ  kept on inviting him to say that sentence while the other two kept on stopping Abu Talib. Finally,

the last thing he said to them, "I am on the religion of 'Abdul Muttalib," and refused to say: None has the right to be worshipped except Allah. On that Allah's Apostle said, "By Allah, I will keep on asking Allah's forgiveness for you unless I am forbidden (by Allah) to do so."

So Allah revealed:-

'It is not fitting for the Prophet and those who believe that they should invoke (Allah) for forgiveness for pagans.'

(Surah at-Toubah-113)

And then Allah revealed especially about Abu Talib:-

'Verily! You (O, Muhammad) guide not whom you like, but Allah guides whom He will.'

(Surah Qasas:56) Sahih Bukhari Book, 60, Hadith, 295