Since model factories create in-memory objects, because of big memory usages it is not suitable for large seeds.

But you can use Faker for data generation:

use Faker\Generator as Faker;
class PostSeeder extends Seeder
{
    public function run(Faker $faker)
    {
        $users= collect(User::all()->modelKeys());
        $data = [];

        for (i < 100000; $i++) {
            $data[] = [
                'body' => $faker->text,
                'image' => $faker->imageUrl(),
                'user_id' => $users->random(),
                'created_at' => now()->toDateTimeString(),
                'updated_at' => now()->toDateTimeString(),
            ];
        }

        $chunks = array_chunk($data, 10000);

        foreach ($chunks as $chunk) {
            Post::insert($chunk);
        }
    }
}