Final answer:
The expansion of the Arabian Peninsula into Africa stopped due to the lack of value perceived by the Byzantine and Persian Empires, shift of focus towards Europe, and the ability of the local population to reclaim independence. The Arab expansion was driven by political and military objectives, and their occupation was often superficial. Islam also diffused into North Africa and Europe through invasions and trade.
Step-by-step explanation:
The expansion of the Arabian Peninsula into the southern boundary of Islamic lands in Africa stopped due to various factors. One reason is that the great Byzantine and Persian Empires to the north did not see much value in dominating Arabia, as the region appeared as a backwater with few resources. Additionally, after Islamic forces successfully invaded the Iberian Peninsula in 711, their focus shifted to Europe, and the Arab armies continued their sweep across North Africa, occupying major towns and advancing as far north as Narbonne, France.
The Arab expansion was primarily driven by political and military objectives, not religious conversion. The Muslim forces had a highly mobile fighting force and benefited from the stationary nature of the neighboring empires. However, their occupation in many cases was superficial, and often the local population was able to reassert their independence, resulting in the Arabs having to reconquer the same territory multiple times.
The expansion of Islam also diffused through North Africa and the Berber people of the Maghreb, as well as into Europe through the Moors who invaded Spain in 711. Islamic influence thrived in Iberia for a time but was eventually pushed out of the peninsula.