Content type entities are marked as syncing during migrations

Content Entities supporting revisions (eg. node) are marked as syncing during migrations and as a result, new revisions are not created during migrations.

If your migrations need to create revisions, implement hook_entity_presave() or hook_ENTITY_TYPE_presave() to force revision creation, such as the following example.

/**
 * Implements hook_entity_presave().
 */
function mymodule_entity_presave(\Drupal\Core\Entity\EntityInterface $entity) {
  if (($entity->getEntityTypeId() == 'node') && $entity->isSyncing() && !$entity->isNew()) {
    $entity->setNewRevision(TRUE);
    $entity->isDefaultRevision(TRUE);
  }
}