In general, insurance companies like to reduce risk any way they can. Eliminating coverage at policy renewal is one of the many methods used.
(And, naturally burying the changes in the middle of coverage details.) Usually, no change summary was included.
Liability and coverage concerns for model aircraft was undoubtedly caused by the on going UAV/FPV/Drone debate.
I can remember when motorcycle insurance coverage and full size rental aircraft liability coverage were the subject of similar reductions in coverage.