Timing can make the world of difference in context though, Cube absolutely would have had the money to trademark (G)I-dle closer to around their debut and no one really would have cared because (G)I-dle wouldn't have established their own public image and would have been known for being from Cube.
Going for the trademark now though feels disingenuous and only to mess around with (G)I-dle because the girls have an established public image and aren't just known as a Cube group and depending on just how long is left on (G)I-dles contracts there's a chance Cube gets rejected since this is exactly what Source Music tried with Gfriend which got denied for this exact reasoning.