Why were Muslims not affected by the the Qur’an as much as the Quraysh infidels and Umar ibn al-Khattab, may Allah be pleased with him, were?

The Quran has a profound effect on those who understand its language. Anyone who hears it with a heart that is not defiant or arrogant may be influenced by it and embrace Islam. As for Muslims, they are affected by the Quran by contemplating it with present hearts, certain of the truth of what is within it. Allah has warned against hard-hearted people who are deprived of guidance by the Quran and its influence, and He has forbidden believers from resembling those among the People of the Book whose hearts have hardened. The Quran has emphasized the importance of contemplating its verses, reflecting on their meanings, and acting upon them, and not merely reciting its letters.