According to some Wikipedia research “De-orbiting a geostationary satellite requires a delta-v of about 1,500 metres per second (4,900 ft/s), whereas re-orbiting it to a graveyard orbit only requires about 11 metres per second (36 ft/s).”

https://en.m.wikipedia.org/wiki/Graveyard_orbit

While theoretically possible, it is a lot easier to put a "spare" 1500-2000m/s of delta v and fuel tankage on a Kerbal spacecraft than in real life. Unless we invent a magical ion thruster with a specific impulse of 30000 nobody is going to put enough fuel on a Geostationary telecom satellite to lower its perigee below 100km at EOL. That same fuel is better used for station keeping and to extend its service life.

The Kerbal way is to remember that to lower your orbit, you have to slow down, and to slow down requires propellant. You're moving really, really fast in a geosync orbit, so slowing down to lithobrake your satellite would require a _lot_ of propellant.

Conversely, to raise your orbit, you have to speed up. And since you're only going up a little bit, you only need a little bit of propellant.

requires a huge amount of fuel for a geo-stat-sat to get back down.