I figured out why the onInit event is not triggered.
The Smart UI version I tested is 15.2.8, while the example on CodePen is using version v14.1.2, which is a different version.
When I tested it with version 14.1.2, the onInit and onRender events were triggered, but when I tested it with version 15.2.8, the events did not trigger.
Is this phenomenon a bug, or is there another reason?