Why was it insure instead of ensure in the Preamble?

To ensure means to be careful to preserve and protect while to insure means to guarantee against loss. An insurance policy pays reparations if the thing it guarantees against loss suffers loss. I believe the founding fathers were well-educated men and would not have preserved a document that substituted insure for the intended ensure. We should not rewrite what has been written but understand the meaning as written. Because the document the preamble was introducing was to be the law of the land, but had not been ratified and this was not yet the law of the land, if this had been an error there would have been plenty of time to correct the mistake. No, the preamble got it right in that it looked forward to the establishment of a system of law that had never before existed and the founders felt that reading the Constitution in a way that would best fulfil the intent laid out in the Preamble would insure that peace would be an integral part of the liberty upon which the nation was being founded. After all, isn't this what forms the basis for the idea that all men are created equal and that they are endowed with their Creator with certain unalienable Rights and that among these are life, liberty and the pursuit of happiness. If domestic tranquility were not insured, it could be broken with impunity and if it were to be constantly interrupted, how could life, liberty and the pursuit of happiness, endowed by God, be preserved?