Why does my motor run at a high rpm when cold?

Its a 2000 ford crownvic, on cold starts, it idles at around 1,700 and on warm its at like 900 rpms

Because the idle control system senses that it cold and raises the idle rpm.

The automatic choke causes that. Don't worry about it.

It is not unusual for an engine to run at higher rpm when the ambient temperature is below freezing and then for it to drop back to normal. I'm not sure if 900 rpm is your proper warm idle speed, it might be a little high.
If you are living in southern climates (Texas, California, Florida, etc.) and this is happening, I would recommend a trip to a mechanic. Short term, you won't be doing much damage but I would be concerned about out long term situations.

Because it is programmed to do so. At initial start the idle control will raise RPM over a thousand. After 15 to 20 seconds it should begin to settle under a thousand.

This is a design system. Any engine running 'cold' at idle speed has high friction levels e.g. Thick cold oil. The drag factor mainly stalls an engine thus it will not operate at such low speeds until oil thins and drag factors reduce to normal.
as it gets warmer and runs freely it will settle to its normal operating region using either automatic choke or electronic controls. It will not adversely affect engine.
we may note on initial start when we crank speed surges then settles down. This is due to extra fuel being pumped in to aid starting. As soon as it runs the extra fuel is cut off back to whatever our system demands based on ambient and engine temperatures. Sensors dictate speeds in combination with our electronic cars main unit.
however for really old engines where a manual choke is used ( classic and historic cars and trucks) the choke is controlled by driver and thus engine speed will stay high if driver does not return choke to off position.
driving with choke out considerably raises fuel usage and emissions ergo automatic systems developed.

Most motors do that. It's to help warm it up and to prevent stalling. It's controlled by the idle air control valve.

Warm up cycle

Because more fuel is fed to the engine while it's cold.

Its redulas to run that high rpm cold, bad for a older engine with a weak oil, hardly any oil on yet running 1700 rpm, what I do is drop it in gear 3 minutes till its down to 900 Rs, just may save your engine.

Its redulas to run that high rpm cold, bad for a older engine with a weak oil, hardly any oil on yet running 1700 rpm, what I do is drop it in gear 3 minutes till its down to 900 Rs, just may save your engine.