U of Utah scholar discusses the current scholarship on the topic.
Two key points:
#1) No sources appear on Islam till 200 years after Muhammad was said to have died. That is, the Koran as we know it today wasn’t written during the time Muhammad was claimed to have lived.
#2) Islam was hugely influenced by Christian roots present in Arabia before the Koran was written. According to the Koran, Muhammad was surrounded primarily by pagans.