Be Hordak:
>You've all but conquered a planet but the pesky Rebels are congregating in a large forested area. You can't find them for some reason but they ARE within laser canon range, apparently.
>A poncey Blond jackass and his muscle bound "friend" show up looking for the princess you kidnapped years ago, and for the first time things are going south for your world domination plans.
>Rather than just building a giant fuck-off laser cannon or getting all of your laser cannons aimed to the woods (since you obviously don't need them for resources or anything) you build what amounts to a giant gravity gun that will pick up the woodlands--and deposit the *entire* forest in a Bermuda Triangle "no one ever returns from this place"
Okay things are kinda dumb at this point, but to be fair, throwing all of your enemies into an eternal magical maze to torture them for eternity is kinda baller if you want them to suffer, which we can assume Hordak does. HOWEVER:
>Gravity canon is hard to power. Rather than funnel all of the Fright Zone's energy into powering it, you decide to throw all your prisoners/slaves/serfs/PoWs into a life energy sucking device that...slowly... almost impossibly fills the device's power gauge.
>Luck out and throw He-Man into the machine, giving you two fully charged shots for it. Forget to lock up obviously magical swords and the princess you kidnapped finds out she's a super heroine, frees/re-powers He-Man and they wreck your shit...WITH A FUCKING ROCK.
>Apprently built backdoors into the device so that when it's smashed, all the energy goes back to the rebels you captured, and they escape, thus arming the rebellion with more man power.
In conclusion, Hordak got REALLY stupid and over confident after her rolled the planet.