iCloud

I needed to free space on my iPhone. I imported all of my photos to my mac to the photos app. I then deleted all of my photos from my iPhone. I confirmed all photos were on the photos app on my mac before I deleted them from the iPhone. Two days later they were instantly deleted from my mac. My iPhone and my mac are set to back up to the iCloud. I am guessing when I connected to the internet on my computer (I usually have internet off) it deleted the photos from my mac because they the same images had been deleted from my iPhone and they were both set to back up to the iCould. This makes no sense to me because the point of the iCloud it to back up your data so why would it delete it from a device such as computer? I also deleted the photos from the Recently Deleted on my iPhone as I was trying to free up space. Very frustrating. 4000 photos gone. Is there any way to get them back?