Why did the framers agree on this length of term of supreme court justices?

The framers of the Constitution agreed on lifetime terms for Supreme Court justices to ensure judicial independence and protect them from political pressures. By granting justices tenure "during good behavior," they aimed to insulate the judiciary from the whims of the electorate and legislature, allowing justices to make impartial decisions based on law rather than popular opinion. This structure was intended to uphold the rule of law and maintain a balance of power among the branches of government.