Short answers, pulled from the story.
Arab merchant ships began arriving at the Malabar Coast of India in the early 7th century. These traders had visited the region long before Islam emerged in Arabia, establishing trade routes that linked South Asia to Southeast Asian ports.
The Cheraman Juma Mosque in Methala, Kerala is thought to have been constructed in 629 CE under the mandate of King Perumal of Chera dynasty. Historical sources suggest this structure may be the first mosque built in India though some historians argue for an earlier mosque in Gujarat between 610 and 623 CE.
Popular tradition states that Islam was brought to Lakshadweep islands by Ubaidullah in 661 CE with his grave believed located on the island of Andrott. This event occurred during a period when numerous Jats in Sindh embraced Islam under the influence of officers from Ali's army.
More than 650 million Muslims live across South Asia forming approximately one-third of the region's total population. About one-third of all Muslims worldwide reside within this geographic area making it home to the largest Muslim population globally.
Richard M. Eaton has described how Sufis played an important role integrating agricultural settlements with larger contemporary cultures across West Punjab and East Bengal. These areas developed into regions where Muslim majorities eventually formed after centuries of settlement patterns.