Al-An'am (The Cattle)
Surah 6 · Verse 107
And had Allah willed they would not have associated partners (with Him) and We have not made you a protector over them nor are you a trustee over them.
Allah (SWT) has power over everything had He willed people would not have associated partners with Him, He has not done so therefore there is polytheism. Prophet Muhammed (PBH) is not a custodian, monitor or trustee over people to make them believe in Allah (SWT), therefore the responsibility of their polytheism is not on him.
