All that energy is being send to the ground instead of used.
No it's not. This classic misconception is probably the origin of all these "harness the lightning" ideas.
Actually, the voltage across the ground is insignificant compared to the lightning itself. Instead, imagine that the lightning is a tungsten filament, or lightning is like the resistor connected between two HV terminals. With a hot tungsten filament ...would we say that all the energy is being sent into the wires and therefore wasted? No, it's being sent into the hot filament, not into the connecting wires. (Current is not an energy flow. That's the key concept. The path for current is in a closed circle, while the path for energy-flow is one-way: into the lightning plasma itself.)
During a lightning strike, how does the energy flow? Cloud-ground lightning is just a spark between two large "capacitor plates." The energy starts out as strong vertical e-field between the cloud-base and the Earth; between the two plates. During the lightning bolt, energy in the air below the cloud is flowing inwards towards the lightning. The energy-flow looks like a shrinking cylinder, with the lightning at its core. Energy in the wide-spread e-field ends up as energy in the tiny region of hot plasma (and then becomes emitted light and sound, and some hot air.)
If you see a lightning bolt, that means the energy is already wasted in powering the bolt. The current in the ground may be enormous, but the wattage there is miniscule.
In other words, if we want to harness lightning, we have to get rid of the lightning bolt, and replace it with some sort of energy-absorber which is connected to some sort of energy storage device. No huge flash, no noise, no miles of "bulb-filament made from plasma."
Instead, look at all that silent invisible e-field energy starting out between the cloud and ground: the two enormous capacitor plates. We want the field-energy to flow into a small point-like absorber on the ground. NOT flow into a miles-long vertical plasma-filament. So, to solve the problem, just tell everyone how to design a fairly tiny machine to efficiently suck the energy out of a capacitor where the plates are two miles wide and a half-mile apart.
Here's an 'easy' solution: build a tower that's a couple miles tall, and mount a metal sphere on top that's roughly the size of a thunderstorm. Then, when it passes through a moving storm, a major portion of the storm's electrical energy cam be collected but without wasting it as a mile-tall streamer of incandescent plasma.