But presumably the courts can?
There is no reason the courts can't see them now, but it appears the Justice Department have been complicit in the coverup.
The courts can't just decide to show his tax returns.
THe situation is basically that Cy Vance and Congress have seperately issued subpoenas to Mazars, Trump's accountants, to hand over his tax returns.
Trump has sued to stop that subpoena and that's been stuck in the courts for 2 years.
When Trump stops being president, Congress no longer has the valid reason for demanding his tax returns.
Cy Vance still does, but he's been trying for a long time with no success - although it's possible that the SC stops backing Trump now they know he's toast.