What just happened? Help needed.

[airbrakes53]

I purchased Kent high speed route. After the 826 meg download it started an install process. Long story short it completely erased my 22 gig railworks folder! Why in the world would it do something so stupid? I know it's touted as a stand alone but it is supposed to look and act like regular DLC if you already own railworks. Yes I have a backup and in 3 1/2 hours it will be copied back off my external drive. But what's going to happen when I verify cache to pick up my newer purchases? I hope someone can shed some light on this so it won't happen again. I know some here purchased the route. Did I miss something? I did notice after the download it asked where I wanted to install it. It defaulted to the steam folder. Should I have installed it somewhere else. Why don't they just have 2 purchases? One for current owners and then the standalone. I would appreciate any insight on this.

Thanks