I was surprised how fast SCOTUS rejected the Texas case, but it has dawned on me that if almost all justices wanted to hurt Trump this is the exact opposite of what they would have done. They could have dragged it out until Monday at least, or even longer, beyond the date of the electors voting.
Instead of that, we got the rejection very fast. And the explanation as to why it was rejected was included in it, which helps anyone who wants to file a new lawsuit that is "corrected". Just as Sidney Powell did in all four states, by the way: https://twitter.com/SidneyPowell1/status/1337597433283571712. And the ruling came before the weekend, which gives two extra days to work on the new cases.
And if you check the ruling it even mentioned that the standing thing was the only detail they have ruled on, as ruling on any other details - such as the unconstitutionality of the actions taken by the four states - was moot.
Just food for thought.
You perhaps unwittingly hit it on the head. The SCOTUS literally can not rule on a disagreement between states.. until there is standing.
Intentionally or unintentionally, it was a test run. And the OP highlights why we remain hopeful: the SCOTUS turned it around in light-speed time. They know.