I don't understand where you are coming from, why did the judges not investigate the letter first before issuing a very one sided controversial verdict, as a matter of fact it was the dubious supreme Court judges violated article 69 of the constitution.
While SC has no ability to judge the letter at it's own.
And also ,SC cannot consider it an issue on the basis of one sided Conjectures/Claims of PTI.
SC could can only give a judgement due to any letter, if any Agencies of the State comes to it along with its report of investigation, which proves that really the opposition was a part of any conspiracy.
And Imran Khan failed to persuade any Agency (even those who were under his direct command) to prove any conspiracy against him and his government on the basis of that letter.
So, on what basis do you demand the SC to stop the democratic process in Pakistan?