Alternately, let's say the Worm entities do arrive in 1980, as scheduled. Let events proceed as in canon for nearly two decades.
Then, in 1999, Lavos erupts from beneath the earth and sprays destruction around the world.
He hasn't manifested before that for at least a thousand years, probably more like 1400. The odds of the entities having looked far enough back to even notice he was there, when gathering information to make their plans, seem extremely limited.
Their endgame is a good 300 years away, and requires a sizable human population for most of that time to really get things going properly. Having most of humanity wiped out a bare twenty years in is not going to make them very happy.
Lavos also screws with time by his very presence - and their own time-travel capabilities appear to be quite limited. What effect the time-traveling people trying to deal with Lavos may end up having on events is far from clear.
(Inspired by the fact that Lavos and the Worm entities seem to have superficially similar lifecycles. For that matter, there are some similarities to Jenova, as well...)
Then, in 1999, Lavos erupts from beneath the earth and sprays destruction around the world.
He hasn't manifested before that for at least a thousand years, probably more like 1400. The odds of the entities having looked far enough back to even notice he was there, when gathering information to make their plans, seem extremely limited.
Their endgame is a good 300 years away, and requires a sizable human population for most of that time to really get things going properly. Having most of humanity wiped out a bare twenty years in is not going to make them very happy.
Lavos also screws with time by his very presence - and their own time-travel capabilities appear to be quite limited. What effect the time-traveling people trying to deal with Lavos may end up having on events is far from clear.
(Inspired by the fact that Lavos and the Worm entities seem to have superficially similar lifecycles. For that matter, there are some similarities to Jenova, as well...)