Why did Makkah merchants and relivious leaders oppose Mahammad and his message

These merchants/religious leaders felt threatened by Mahammad's message that supported only One God and no idols. Most of these men obtained their wealth as migrant clans traveled to Mecca to worship their clans god or gods. If there was only One God and He could not be represented by an idol, this would discourage travel to Mecca and all revenue from traveling clans would potentially cease.