The bumps in a depiction of the geoid aren't just exaggerated. They are vastly exaggerated.
The Earth is very close to spherical, with the largest deviation from spherical being the Earth's equatorial bulge. The North Pole is 21.4 km closer to the center of the Earth than are places at sea level at the equator. That's a tiny fraction (about 1/3 of 1%) of the 6378.137 km equatorial radius of the Earth. If you were playing with a volleyball that was out of round to this tiny extent, you would not notice it.
The next largest variations are mountains versus deep sea trenches. The deepest part of the Mariana Trench is 10.994 km below sea level while the peak of Mount Everest is 8.848 km above sea level, a difference of almost 20 km. These are local rather than global variations. The variations in a volleyball due the seams and little blemishes in the plates are much larger.
What the geoid attempts to measure is mean sea level. An Earth devoid of mountains, deep sea trenches, and continents would be covered by a globe-spanning ocean. The Earth's shape (mean sea level) would be very close to an ellipsoid if the underlying rock had the same density profile from any point all the way down to the core-mantle boundary. The equatorial bulge would still be there; this bulge results from the Earth's daily rotation.
The geoid height variations depicted in various images show the deviation of mean sea level from that idealized ellipsoidal shape. These variations are very small, ranging from about -100 meters to +100 meters. Notice how much smaller that range is compared to the variations between the deepest parts of the ocean and the tallest mountains or between the equator and the North Pole. The only way to depict these small geoid height variations graphically is to exaggerate them, and not just a little bit, but many, many times over.
