One benefit of using requireJS is that it can ensure that the js module is loaded in the order of dependencies you specify.
Back to your code, define is used to define a module and indicate that the module depends on XyEason. Therefore, requireJS will ensure that the callback function, which is function(XyEason), is executed after XyEason is loaded. The execution of the
callback function is asynchronous, and the load event occurs when the page is loaded. By the time this code is executed, the load event has already been triggered, so it will naturally not be executed.
Your code is equivalent to the following paragraph

setTimeout(function(){
  window.onload = function(){ alert("load") } //永远不会执行
},1000)

The key point is when you require(). If it is after the onload event, it will definitely not be triggered. I hope it can help you.