Why do some of the victims of the Holocaust feel possessive of its study?

because if you were not there, then you can only try to imagine what it was like, even those who lived through the same time period and (for example) escaped the Nazis and lived in safety cannot fully understand the period.

The problem is that now, in the present day, for the study of the Holocaust to proceed it is necessary for people who were not victims (or even alive during that time) to continue the work, so as to keep it uo to date and accessable to the twentyfirst century audience.