It's actually thought that Kessler syndrome is kind of already happening right now, which is why there's a lot of push right now to try to de-orbit the very large pieces of debris, so they can't act to form further debris.
The reason it's a scary outcome is because it's an exponential. It can look like an isolated incident or incidents, then the next day be not practically stoppable.
I’m sure I’m missing something but it just seems like a no brainer to make the deorbit process speed up with something relatively failsafe, as opposed to hopefully/maybe saving a bit of fuel to push it that way eventually
And you can't just wave around "hacking the control plane". Russia's been trying to interfere with Starlink for a while and they haven't had any long term success. And finally, even if the did somehow get access to the control systems at SpaceX, the satellites can't de-orbit quickly. It takes weeks to de-orbit, over which time they could be commanded to reverse course.
The effort of getting a ballistic trajectory that peaks at 500km is a lot smaller than reaching a stable orbit of that height. And just like WWII aircraft you don't need to hit them, just produce enough shrapnel in their vague vicinity.
The biggest hurdle is the universal international condemnation you would receive for such an act
