I once had a collection of poker-related software that did in the low 6 figures per month. Unfortunately recent government actions kicked that in the nuts.
Unfortunately it's more because my customers are. If I could just move I would have to have maintained that level of income. It's hard to pass up a few hundred grand a year for not much work.
I believe it's more that the majority of the market was playing on the sites that were recently shut down. Less online players and play opportunities would correlate to a reduced interest in playing aid software.