I have already done some research, going to the book by Kasper that you quoted. There it is pretty obvious that your conclusions are unwarranted. For goodness sakes, they are explicitly denied by Kasper!
Now you point to the internet, as if everything on the internet is true. The earth is flat, global warming isnt true, global warming is true, etc. Anyone can find almost any position defended on the internet. You repeat arguments that have been used before, against Kasper and others. They are tired, unconvincing arguments that rarely portray the attacked party charitably.
The paragraph you quote here is muddled. The first sentence is likely based on someone saying "People did not understand the Resurrection until after it happened." Or something like that. That is not controversial unless you want it to be. In the 2nd sentence whomever relies on the ambiguity of history, ie Kasper says the Resurrection cannot be verified by historians but it is read as "it did not happen."