Allah (swt) is addressing the believers not to take the disbelievers in Mecca as allies thinking that they own the power rather than the believers.
( أَتُرِيدُونَ أَن تَجْعَلُوا لِلَّهِ عَلَيْكُمْ سُلْطَانًا مُّبِينًا … ) (…Do you wish to give Allah against yourselves a clear case?): A clear case that He decreed on the hypocritical people, whom He described to you, and told you of their fate.