What is the reason for the abundance of disagreements in Islam, and what implications do these disagreements have for the possibility of unifying the madhahib (schools of thought)?

May Allah facilitate your entry into Islam, for it is the happiness of both worlds and salvation from misery. We advise you to embrace Islam immediately without any impediment, for death may come suddenly, and you must make the knowledge of the truth your primary concern. The source of truth in Islam is the Quran and the Sunnah, and the fundamentals of faith are clear within them. The disagreements among Muslims do not negate the fact that Islam is the true religion, for no nation is free from disagreements, and ignorance and whims may cause them. Islam calls for unity, and one must differentiate between the religion and the actions of its followers. The Companions did not disagree on the fundamentals of the religion; their disagreements were on matters of ijtihad (independent reasoning). Juristic disagreement is not blameworthy as long as it does not lead to bigotry and discord.