The State Legislatures won't take action until there are Court rulings calling vote totals into question.
Those rulings will come.
I suggest you read Justice Alito's orders in the Pennsylvania case.
This case is yet to be decided on the merits, but it is likely that the US Supreme Court will rule that the Pennsylvania Supreme Court had no authority to water down the Pennsylvania Legislatures rules for mail in voting for Presidential elections.
If they do, then the entire vote in Pennsylvania will be tainted because it is impossible to find those ballots which had defective outer envelopes (missing matching signatures or valid postmarks).
I believe that the Supreme may well decline to hear the case AGAIN. I believe that the Republican-led state legislatures in states that were called for Biden will use that as an excuse to claim that they have no proper recourse except to replace Biden electors with Trump electors. This will "legally" and "constitutionally" give the victory to Trump. All it requires is the total lack of integrity that has already been demonstrated by the Senate with "the McConnell rule" and not even calling witnesses in an impeachment trial that their majority could easily prevent from convicting.
More details at https://peakd.com/trump/@digital-wisdom/will-a-50-state-united-states-exist-in-2022
You are misunderstanding the first ruling.
The Supreme Court did not decline to hear the case.
They split 4-4 on whether to issue an urgent interim injunction to over-ride the PEN SC's decision before a full hearing on the merits.
They likely felt that it probably wouldn't matter because the election would be decided on other states.
Courts often decline to give urgent injunctions - it says little about the merits of the case as merits is not the main determinant - balance of convenience is.