why java.exe is removed from c:\windows\system32 in jre 8?
Leave it all as it is.
I was going to write a blog about this and changes that Java have made, specifically around the fact that now the java.exe is no longer in the system folder. But you can call java from a CMD because it adds its location, as you have pointed out into the path statement (C:\Programdata\Oracle\Java\javapath).
Are you trying to run a CA during the java install??
If you are you might need to get your timings right. Since the wonderful Java MSI 'isn't', its just a bunch of CAs, you will need to wait until the install has actually finished, then written the change to the Path statement, and then you can call java 'from anywhere'. The reason it works if you copy the java.exe into the System folder is that it is already loaded into the path statement.