the President does have, as part of his oath of office, defending the Constitution, which presumably could require him to stop an insane SCOTUS out to wreck everything

That came up in one of the Federalist papers:

The judiciary...has no influence over either the sword or the purse; no direction either of the strength or of the wealth of the society, and can take no active resolution whatever. It may truly be said to have neither FORCE nor WILL but merely judgment; and must ultimately depend upon the aid of the executive arm even for the efficacy of its judgments.

--Federalst No. 78

Andrew Jackson infamously ignored a Supreme Court ruling in Worcester v. Georgia.