While the .onclick property is one way to add a click event listener to elements, it's not the only way. Another way is via .addEventListener(). When an event listener is added to an element via .addEventListener(), the onclick attribute/property doesn't update to the event handler function. The .onclick property is only set on an element if you're using the onclick="" attribute or if the code has set the property elem.onclick = function() {...}, which nowdays isn't very often.

Chrome does provide you with a way to find the event handlers on different elements. When you're in your developer tools, you can select the element you're interested in, click "Event Listeners" in the right-hand pane, find the event you're intrested in, in this case that's the "click" event, and then look for your element:

Your element happens to have an event associated with it, but this might not always be the case. As the comments on your question have pointed out, you can sometimes run into cases where there is no click event handler on your specific element, but rather, it is added to a parent of that element. In this case, when you click on your element, the event propegates/"bubbles" up through the DOM, eventually reaching your parent element with the click event listener. The event handler on the parent can then see what element was originally clicked, and can then perform some actions based on that. This is known as event delegation, and is one of the reasons why you might not always find an event tied to your element even when looking in dev tools.