Is Muhammadism (Islam) similar to the pagan idolatrous religions of the east?
No. Muhammadism (Islam) is certainly not akin to the pagan idolatrous religions of the east. The context distinguishes it from those pagan idolatrous religions that have always predominated east of the Euphrates River, placing it instead with Judaism and Christianity west of that boundary.
Les explains that every pagan mythological religion traces its roots to the Tower of Babel on the Euphrates River. He notes the Euphrates is the great boundary between east and west. East of the Euphrates has always been predominantly pagan idolatrous religions. West of the Euphrates, he lists Judaism, Muhammadism, and Christianity. He specifically states that Muhammadism is certainly not akin to the pagan idolatrous religions of the east.