In order to understand "Why did Muhammad PBUH go to Mount Hira?" one needs to know the conditions and situation at which He lived.
To have an idea about the conditions and situation of that time just think about this "People buried their first-born girls while they (girl babies) were alive just after they are born". Can you imagine this? And doing so was known as a heroic act. And too many other things. They were simply wilder than animals.
Prophet Muhammad(peace and blessings be upon him) used to go to the Mount Hira and look for a solution for this problem. He used to go there for about 2 years after which the Archangel Gabriel came to him and brought the first revelation of the Holy Qur'an which is as follows:
"
In the Name of Allah, Most Gracious, Most Merciful.
[96.1] Read (Prophet Muhammad) in the Name of your Lord who created,
[96.2] created the human from a (blood) clot.
[96.3] Read! Your Lord is the Most Generous,
[96.4] who taught by the pen,
[96.5] taught the human what he did not know." (Qur'an 96:1-5)
In conclusion, he went there to think about a solution for the problems of that time...
Sincerely
The last prophet of Islam Hazrat Muhammad Mustafa (May peace be upon him) used to visit Cave Hira and spend even weeks in solitude and meditation. It was there that the Arch Angel Hazrat Gabriel (AS) first came to him and revealed the first verses of the last heavenly Book the Qur'an: Translation:
Read in the name of thy Lord Who created; created man from a clot (of congealed blood): Read and thy Lord is most Bountiful, Who taught (the use of) the pen, taught man that which he knew not. (Quran, 96:1-5)
He was commanded by Almighty God to proclaim ONENESS of Almighty God.
