Why is ElevatedButton getting stretched and becoming a background?

Question

I'm new on flutter and I don't have an idea why ElevatedButton stretched and become a background. I just want a simple button. How can I solve this problem? Here's the image below:

Here's my code

@override
  Widget build(BuildContext context) {
    return Scaffold(
        body: Center(
          child: ElevatedButton(
            onPressed: () {
              Navigator.pop(context);
            },
            child: SafeArea(
                child: Center(
                    child: Column(
                      children: [
                        Image.asset(
                          'profile_image.jpg', height: 150, width: 150,),
                        const SizedBox(height: 15,),
                        Text("Hello World"),
                        const SizedBox(height: 15,),
                        const Text('Go back'),
                      ],
                    )
                 )
              ),
           ),
        )
     );
   }
}