titan said:
Since two (and maybe more) of the judges thought it should be considered
Again, wrong.
Alito and Thomas were simply asserting their (minority) viewpoint that the Supreme Court is
required to rule on all cases brought by one state against another state. Per Thomas' earlier dissent in an unrelated case, the point of view is that the Constitution requires SCOTUS to issue rulings in legal disputes amongst the states.
In actual practice, it is not unusual for the Court to simply refuse to hear such cases (for example, South Dakota filed suit against Colorado a few years ago claiming that the legalization of marijuana in Colorado would lead to increased crime in South Dakota, in essence). The Court declined to hear the case and issued no ruling.
Apart from high profile publicity stunts like this one, most of the Court's "original jurisdiction" cases involve water rights or border disputes. The justices tend to hate these cases because they require appointing a special master to investigate facts (which SCOTUS never does in any other cases, because establishing facts is the job of the trial court), and usually the resolution of the case is of no interest to anyone other than the involved parties. They have no interest in signing on to a legal doctrine that would oblige more of their workload to be devoted to such disputes, which is what Alito and Thomas are advocating.
It is nothing more than the view that if state A sues state B, the Constitution obliges the Supreme Court to respond. Although the minority viewpoint expressed by Alito and Thomas is sincere, it has nothing to do with the particulars of this case at all. It is just that as strict textualists, they believe that this is what the Constitution requires and stand by that belief in all cases.