How do Iblis and the wicked derive their strength and success, even though divine grace is from Allah?

Indeed, Iblis and others possess abilities through which they act and for which they will be held accountable. These abilities are constrained by Allah's power, for nothing occurs except what His knowledge and decree have preceded. No one is afflicted by good or evil except what Allah has ordained for them. Weakness of faith leads to the dominance of Satan, while adherence to the religion is a cause for protection from him.