When you view a RAW image, what you are actually seeing is a conversion of a RAW image. This is true whether you are looking at it on the screen on the back of your camera or on your computer screen, because the screens themselves are not designed to display more than an 8 bit per color dynamic range. Your camera, depending on model, probably records RAW files in either 12 or 14 bits per color. The designer of the software (or firmware in the case of the camera) that is displaying the image made some assumptions based on an "average" image and this default conversion is applied to the RAW image when it is displayed. Just as it is the case that information is discarded when you convert a RAW image to JPEG, the image as it is displayed on the screen does not include all of the information contained in the RAW file.
When you start fiddling around in Lightroom you are replacing the default instructions applied in camera or on initial display in Lightroom with instructions you have customized to that particular photo. By increasing the exposure four stops, you are telling the program to show the detail in the darker parts of the picture at the expense of the brightest parts of the picture. Notice how the detail in the flames themselves and their reflections on the holder has been washed out? Using tone mapping you could attempt to get some of that detail back by decreasing the level of the highlights without decreasing the overall brightness of the mid-tones and shadows as well. Tone mapping is used to help squeeze as much of the the information in a 14 bit RAW file as we can into an 8 bit JPEG.