App works only with current version but not later

I just since some understanding here and hoping this site is not filled with trolls (maybe get out there and have a life if you are). I use this journal app called Day One and have recently upgraded the version. Somehow the updated version doesn't work with the pop up saying "quit unexpectedly".
I went to preference in the library folder and had to delete a .plist file in order for this updated version to work. NB. the version I used before was working.
I'd like to understand why I had to go through this step for an updated application to work.