The Exposure Triangle is a continuous entity. A change to any value necessitates a change to at least one, perhaps both of the other elements. If we want a higher shutter speed, then either we have to open the aperture or increase the ISO or some combination of the two. When we shoot in full automatic, the camera’s CPU is doing all the work for us based on the meter reading. That’s great, right up until we choose to take a bit more creative control of the triangle.