From the opinion, footnote 15

For example, according to one article, about a month before the Rule was promulgated, the
President tweeted twice that Guatemala was preparing to sign an agreement that would force
migrants crossing through it to apply for asylum there and block them from seeking asylum
elsewhere, including in the United States. AR at 635. But nothing in the record suggests that
those tweets caused a surge at the southern border.

The Cares Act directed the stimulus payments to people who filed a 2018 or 2019 tax return. The payments went to people making up to $99,000 annually. According to the GAO, IRS officials raised questions with Treasury as the Cares Act was being drafted about the possibility that payments could go to people who filed tax returns but subsequently died. However, IRS counsel determined they did not have the legal authority to deny payments to people who had filed a return, even if they were deceased at the time of payment.

Also, Treasury officials noted that the Cares Act mandated delivery of the economic impact payments “as rapidly as possible.” To fulfill this mandate, they used procedures that had been put in place for stimulus payments issued in 2008, and as a result did not use death records as a filter. The GAO noted that in 2013 it had identified weaknesses in IRS procedures that allowed payments to go to dead people, and had recommended corrective action. IRS subsequently implemented a process to use death records to update taxpayers’ accounts to identify and prevent improper payments.
(snip)
But this control was bypassed for the stimulus checks issued under the Cares Act, which “substantially increased the risk of potentially making improper payments to decedents,” the GAO said. It also said that according to a Treasury official from the Office of Tax Policy, Treasury had been unaware that payments might go to dead people.
https://www.washingtonpost.com/us-policy/2020/06/25/irs-stimulus-checks-dead-people-gao/