There is a script that runs daily which detects "suspicious" voting patterns and reverses them; the details about this script are kept secret to prevent people from gaming the system, but it generally detects multiple votes (up or down) which all take place within a particular time frame by one user.
This script is not perfect. I have seen it trigger many times over the years for legitimate votes, and seen it fail to trigger what appeared to me to be blatant fraud. Automatic systems are only so good.
Whether or not this was legitimate serial voting or not, voting behaviour is anonymous by design; in general, there's no way for you to know who did it unless the voter explicitly tells you (and even then, you'd still have to decide whether or not he's telling the truth).
In this case, I don't mind admitting that, yes, I was the one who cast those votes. In the last twenty-four hours, I've cast…forty downvotes or so, across multiple users. That's just how I roll (seriously, just look at my profile. I didn't reach 7.2k downvotes by sitting pretty.) Eight of those were on your posts, and that apparently triggered the serial downvoting script which reversed them.
I stand by every single one of those downvotes, and will continue to do so even if another moderator or a CM chooses to investigate my behaviour. The fact that a good fifth of the downvote-worthy posts I happened to read in just one day all happened to have been written by you really should concern you more; one of the core principles of the Stack Exchange model is that if you want good answers to your questions, you need to take the time to write good questions. I don't send question-quality warnings lightly, and many of your posts have received downvotes and close votes from multiple users in the community, not just my own.