It doesn't surprise me that the .270 Win. is the most popular. I've been shooting one for more than 50 years. Probably because my dad shot one as well. There are a lot of good calibers for deer and getting to be more all the time. What makes a caliber popular? Over time it has to have good ballistics but I also think it's a caliber that over time will do the job and have good access to shells. The .270 is one of those as are most others that are mentioned. Gun writers also play a big part. Jack O'Connor and his writing about he .270 certainly played a part in that gun's popularity. What's the draw with the 6.5 Creedmor? There are other calibers with similar ballistics, some even better, but it certainly seems to be the hot one of the newer choices.
As I mentioned earlier I have been shooting my .270 for many years but have recently developed a real liking to a .25-06 that I received a few years ago. One of the other things that has helped some calibers is the development of some really good bullets that make a real difference in killing power, especially for smaller calibers. Have fun with this discussion as it will never be settled and 10 years from now there will be some new calibers that are no b better than this list, they will just be new and we all like to try something new.