It surely took them long enough to finally make up their minds. From the quotes, it appears that Kavanaugh wanted a ‘better’ case to make a ruling.
I can’t say I totally disagree with him as I think he believes (what with Roberts being the new “squish”) that they’d wind up with a very narrow decision and then not revisit RKBA for another 10 years.

Supreme Court declines to rule on its first Second Amendment case in nearly a decade

The Supreme Court said Monday that it will not issue a ruling in a closely watched case over a New York gun regulation that barred transport of handguns outside the city, including to second homes and firing ranges.

In an unsigned opinion, the court said that the rollback of the rule by city and state officials after the court agreed to hear the case effectively ended the dispute without the justices needing to intervene. 

Conservatives were hoping the court, which has a new 5-4 conservative majority, would use the New York case to limit regulations on firearms further. But the outcome of the case was telegraphed in December during oral arguments, when the court spent little time addressing the underlying constitutional questions raised by the New York regulation.

Justice Brett Kavanaugh, a President Donald Trump appointee who’s known to have an expansive view of gun rights, wrote separately to say he agreed with the court’s handling of the “procedural issues” raised by the case, but urged his colleagues to hear another Second Amendment case “soon.”

Three of the court’s Republican appointees, Justices Samuel Alito, Neil Gorsuch and Clarence Thomas, said they would not have dismissed the case. Alito, in an opinion joined by Gorsuch and in part by Thomas, wrote that by declining to rule in the case the court allowed itself to be “manipulated.” 

While New York City had previously defended its gun regulation in court, once the Supreme Court agreed to review it, both city and state “sprang into action to prevent us from deciding this case,” Alito, a George W. Bush appointee, wrote.

“What about a stop to buy groceries just before coming home? Or a stop to pick up a friend who also wants to practice at a range outside the City? Or a quick visit to a sick relative or friend who lives near a range?” Alito wrote.

Alito’s comments echoed lines of argument raised in December.

The attorney for the gun owners, Paul Clement, had said during arguments that his clients could still be prosecuted for a simple coffee stop under the city’s new rule. But Richard Dearing, who argued on behalf of New York, said there would be no such prosecutions.

The court’s unsigned opinion explicitly declined to address controversies relating to the “new rule” over coffee stops and bathroom breaks.

The opinion also did not engage with the argument raised by the gun owners that they could seek financial damages based on the old rule, instead noting that those new issues would have to be raised first in the lower courts.

The case is New York State Rifle & Pistol Association v. City of New York, No. 18-280.