For example, in California, a Buyer has to actively release contingencies throughout the process.

Lower rates will simply put inflation thru the roof, hurt the housing market by going back to way over asking prices with no contingencies, so making it more unaffordable.

They will typically have funding contingent upon the cleanup being 100% complete and a third party report noting it is clean.

Also, you should only be looking for cash buyers so financing contingencies should not be an issue. 

My offer was rejected in 10 minutes and I was told that no document contingency would be acceptable.So, I am left a bit bewildered -- what I am missing here?

If you are representing yourself, I would advise reading up on various land contingencies.

You should make an offer contingent upon financing. 

I have a giant sheet with hundreds of lines of info: OpEx, transaction costs, holding costs, contingencies, rent forecasts, etc.

You will want to make sure that you are aware of any and all deadlines and fully understand contingencies.

If someone has a credit below our threshold, but everything else looks solid, then we will sometimes offer a credit contingency plan where we help offset the low credit score risk with a double deposit.