The Git commands that are most useful 95% of the time just didn't seem that hard to learn, IMO. It's not worth wasting memory for the other 5% of the time because I'll probably need to check the man pages anyway.
For those that I point to Git now, especially those that are semi-technical, it's really useful to also point them to a nice intro. As with all new things, lowering any barrier to entry is usually a good thing.
Git's UI being complete shit probably helped there.
We also had a lot of problems with what I think of as "Linux Arrogance" - the person who took the lead on rolling out git refused to even try to help anyone not using git in a bash shell, which is an issue when all the devs are .net developers with no cygwin experience.
Once you can figure out the commands you need to use git is very nice, but it's a nightmare to start and requires a big mental step backwards to teach someone with no exposure to it.
I guess the longer you've used a centralized approach, the more "intrenched" that way of thinking is, and the bigger the mental shift has to be.
Unlearning the old can be much harder than learning the new..