Trampolines are obscenely high risk and injuries are very common. On top of that, if a neighborhood kid comes in to your yard and breaks their leg on your trampoline, your home owners insurance is going to be involved.
The tortable aspect (compensation for causing personal injury) must also be covered.
In my part of Europe, if someone breaks something while making normal use of your trampoline that would be considered an accident. You would only be liable if you had grossly neglected maintenance on the thing, knew that (or would reasonably be expected to know that), and they can prove that this has caused the injury.