The author could be writing in a different genre and doesn't want to confuse their work with previous novels that might be wildly different. The author could be trying out a more marketable name because their earlier works didn't do as well as they had hoped, or maybe they simply don't like their name and relish the idea of changing it.
None of those were true for me personally. I began publishing under
T. MIchelle Nelson from the beginning. My pen name is a name similar to my real name and a family name, which is why I chose it instead of something cool like Trixie LaReaux, which will be my witness protection name should I ever find myself in that situation and get to choose (although I probably just blew that by posting it online!). To answer why I chose T. Michelle Nelson, well, I suppose I just wanted to keep my anonymity, which in hindsight I'm very glad I did.
Being very realistic and honest, let's face it, I'll never have the recognition of a Stephen King. That's not to say in this day and age where any online presence can result in weird stalkers, I had no intention of putting myself or my family out there. Since 2012 when my first book was published I have received dozens of very strange emails, facebook messages and tweets to say the least. I try to make myself available to answer emails, follow readers back on facebook and twitter and answer any real questions. However, I highly recommend any new author who wants to have a large online presence and market their books as I have consider if they want their real name available to anyone who might read their work or even see them online. I love getting to know my readers, but I do not care for tens of thousands of people who follow me on twitter to have my home address.
Bringing up Stephen King again, think back to MISERY. I behave like I'm dying when I stump my toe. I couldn't handle being hobbled. One interesting thing I've learned over this whole experience the last few years is, you don't have to be super famous to have over-aggressive fans. I would like to reiterate that I do LOVE getting emails from readers, just not the ones who would like to see what my insides look like.
That being said, if you are so inclined and not homicidal, please feel free to drop me a note on the contact page of my website anytime!