Going crazy over onItemClick

…click event handlers outside of the realm of this code block…
And this is exactly your failure. Your code looks wrong.

Try to do it like the following example…

$w.onReady(function () {  
	 wixData.query("TrekGolfTrivia")     
	.find()     
	.then(res => {       
		quizQuestions = res.items;       
		quizQuestions = shuffle(quizQuestions);      
		 quizQuestions = quizQuestions.slice(0, 9);              			
		$w("#quizRepeater").data = quizQuestions;     
	}); 
	$w("#quizRepeater").onItemReady(($i, iData, index)=>{
		$i('#yourButtonIDhere').onClick(()=>{
			displayQuestions;
		});
	});
});

… you do not show the rest of your code, so it is not clear what else you have in your function.