And nothing prevented men from believing when the guidance came to them, except that they said: "Has Allah sent a man as (His) Messenger? (94)Say: "If there were on the earth, angels walking about in peace and security, We should certainly have sent down for them from the heaven an angel as a Messenger. (95)

وَمَا مَنَعَ النَّاسَ

(And nothing prevented men) means, most of them,

أَن يُؤْمِنُوا

(from believing) and following the Messengers, except the fact that they found it strange that human beings would be sent as Messengers, as Allah says:

أَكَانَ لِلنَّاسِ عَجَبًا أَنْ أَوْحَيْنَا إِلَىٰ رَجُلٍ مِّنْهُمْ أَنْ أَنذِرِ النَّاسَ وَبَشِّرِ الَّذِينَ آمَنُوا أَنَّ لَهُمْ قَدَمَ صِدْقٍ عِندَ رَبِّهِمْ

(Is it a wonder for mankind that We have sent Our revelation to a man from among themselves (saying): "Warn mankind, and give good news to those who believe that they shall have with their Lord the rewards of their good deeds")[10:2] And Allah says:

ذَٰلِكَ بِأَنَّهُ كَانَت تَّأْتِيهِمْ رُسُلُهُم بِالْبَيِّنَاتِ فَقَالُوا أَبَشَرٌ يَهْدُونَنَا

(That was because there came to them their Messengers with clear proofs, but they said: "Shall mere men guide us?")[64:6] Fira'wn and his people said:

أَنُؤْمِنُ لِبَشَرَيْنِ مِثْلِنَا وَقَوْمُهُمَا لَنَا عَابِدُونَ

(They said: "Shall we believe in two men like ourselves, and their people are obedient to us with humility!")[23:47]

Similarly, the nations said to their Messengers:

إِنْ أَنتُمْ إِلَّا بَشَرٌ مِّثْلُنَا تُرِيدُونَ أَن تَصُدُّونَا عَمَّا كَانَ يَعْبُدُ آبَاؤُنَا فَأْتُونَا بِسُلْطَانٍ مُّبِينٍ

("You are no more than human beings like us! You wish to turn us away from what our fathers used to worship. Then bring us a clear authority")[14:10] And there are many other similar Ayat.

Then Allah says, pointing out His kindness and mercy towards His servants, that He sends to them Messengers of their own kind so that they will understand what he says and will be able to speak to him directly. If He sent to mankind a Messenger from among the angels, they would not be able to deal with him face to face and learn from him, as Allah says:

لَقَدْ مَنَّ اللَّهُ عَلَى الْمُؤْمِنِينَ إِذْ بَعَثَ فِيهِمْ رَسُولًا مِّنْ أَنفُسِهِمْ 

(Indeed, Allah conferred a great favor on the believers when He sent among them a Messenger from among themselves)[3:164]

لَقَدْ جَاءَكُمْ رَسُولٌ مِّنْ أَنفُسِكُمْ

(Verily, there has come unto you a Messenger from among yourselves)[9:128]

كَمَا أَرْسَلْنَا فِيكُمْ رَسُولًا مِّنكُمْ يَتْلُو عَلَيْكُمْ آيَاتِنَا وَيُزَكِّيكُمْ وَيُعَلِّمُكُمُ الْكِتَابَ وَالْحِكْمَةَ وَيُعَلِّمُكُم مَّا لَمْ تَكُونُوا تَعْلَمُونَ - فَاذْكُرُونِي أَذْكُرْكُمْ وَاشْكُرُوا لِي وَلَا تَكْفُرُونِ

(Similarly, We have sent among you a Messenger of your own, reciting to you Our verses (the Qur'an) and purifying you, and teaching you the Book and the Hikmah, and teaching you that which you used not to know. Therefore remember Me. I will remember you, and be grateful to Me and never be ungrateful to Me.)(2:151-152) Allah says here:

قُل لَّوْ كَانَ فِي الْأَرْضِ مَلَائِكَةٌ يَمْشُونَ مُطْمَئِنِّينَ

(Say: "If there were on the earth, angels walking about in peace and security,) meaning, just as you do,

 لَنَزَّلْنَا عَلَيْهِم مِّنَ السَّمَاءِ مَلَكًا رَّسُولًا

(We should certainly have sent down for them from the heaven an angel as a Messenger). meaning, 'one of their own kind. But as you are human, We have sent to you Messengers from yourselves, as a kindness and a mercy.'