My ethnic background, despite not imposing significant restrictions on my preferences, may have influenced the outcome. Additionally, my friend pointed out that my atheistic/agnostic stance could have further narrowed my potential pool of matches, possibly eliminating up to half of the available candidates.
Back in those days, eHarmony was almost exclusively for Christians, since it was founded by a devout Christian guy. It's a little less so these days, but it still has that reputation and the users there are much more likely to be religious than other dating apps I think. I tried it for a little while about 5 years ago and found it to be a waste of time and quit.