"HAHA you technological dweebs! No more space for you! Now you're going to have to mend your own world first!"
Originally low earth orbit had been wide empty space. Then the Russians came. Then the US. Then the communication companies. Then the microsats, and the kiddie science experiments. It had evolved into a carefully orchestrated dance, with satellites shooting every which-way. These environmental terrorists had just taken it a step further, loading a few microsats with grenades and setting them off. That spread shrapnel at low velocities in all directions from the original orbit (differing only by one kilometer per second). But the original orbit went at right angles to other orbits at about ten kilometers per second, and at those speeds a hit with a single bit of shrapnel was enough to turn any satellite into another burst of shrapnel. After a few weeks of chain reactions, the Kessler Syndrome had set in, with all of low earth orbit a massive uncontrolled shooting gallery. It took out everything.
Geosynchronous orbit remained, but getting there would have to pass through low earth orbit for an hour, and usually that was enough to knock out anything.
Satellite phones? Out. Spy sats? Out. Rogue nuclear powers developing unhindered? No dice, supersonic spy planes still worked. Intercontinental ballistic missiles? Out. Weather prediction? Still fairly good. SpaceX colonizing Mars? Fuggedabouddit.
Right?
SpaceX scheduled more launches after the Kessler Syndrome set in, not less. Instead of aiming their rockets East, to take advantage of the earth's rotation to establish a stable orbit, they aimed them West. And loaded them with payloads of tons of sand. Which they purposely exploded right after they left the atmosphere.
The resulting space sandstorm did not have enough momentum to stay up. It just went up, sprayed all over the place, and fell back down. The shrapnel running into it at ten kilometers per second was sandblasted into smaller pieces. Slower pieces. Which also fell down. The night sky was very colorful for a few nights. Then it faded. Some grains of sand managed to achieve the speed for a stable orbit, but they were highly charged, and the Van Allen belts cleaned them up within a month. Then the night sky was pristine. And SpaceX resumed on its original schedule.
"Amateurs."
20 years later, as the first space elevator was nearing completion, the news raved about the coincidence. How this would not have been possible without having cleared low earth orbit first. Because the low earth orbit satellites would have run into the elevator. A lone investigative reporter revealed that the original eco-terrorists had been funded by ...
200 years later the earth looked almost like Saturn, with a ring of space elevators sticking out in every direction from the equator. Satellites in low earth orbit were strictly forbidden. Geosynchronous too, due to elevator mishaps always passing through that area. Each elevator was a tube of interconnected cables, like a space stocking, with cars riding up and down the outside of the tubes. Earth manufacturing was about taking in raw materials from the asteroids, building them into space habitats, and launching them up the elevator full of people into solar orbit. Space surveillance of earth was done these days from fixed cameras inside the elevators themselves rather than satellites.
Mars, it turned out, was a passing fad. The real action was the dense swarm of powered O'Neil habitats in a fat torus in the space between Mars and Jupiter. From Earth, the torus lit up the night, a constant band across the sky. Unlike Earth's original low earth orbit, the torus had traffic laws. No habitat was allowed to have a velocity that differed by more than 50km/hour from the local Kessler Wind. The Kessler Wind was the average velocity for satellites at that position in the torus. Collisions always cause the resulting debris to have a speed somewhere between the speed of the original two objects. The speed limits meant that high speed collisions did not occur. Debris had an even slower speed relative to the local Kessler Wind, rendering the old Kessler Syndrome impossible. Space junk was cleaned up by old men with space suits and electric fishing poles, sitting outside in the cosmos all day and hoping for a catch.
This was in response to a prompt on reddit.com r/WritingPrompts, "Environmental terrorists artificially activate the Kessler Syndrome, making spaceflight impossible. With the intention of forcing earth to fix it's problems as there is now no escape to Mars."