Getting from here to there can be a mystery sometimes....

I love it when other artists can show their process and I can understand each of their steps and how it led to the next reiteration of their work.  From the laying in to the final touches...each step was carefully thought through with intelligent problem solving.  But I must believe that they have equal number of times where the process is a mystery and they have no idea how they got from here to there.  It certainly is the case for me and perhaps it is due to my relative inexperience in understanding my *own* process.  That said...I was looking at the photographs I took while painting this landscape trying to understand what I did and why.......and I'm baffled.  I have no idea how the final (almost) painting evolved and feels very unconnected to the previous renditions particularly between the last two.  I realize the composition and palette remains the same but the last one is full of totally different brush work and 'style'.   I almost feel as if I simply painted *over* the other paintings with a completely new one. 

How often does this happen to other artists?  Is there a process here that I am just not able to see?