A couple of reasons, I'd wager.
The first, of course, is internalized misogyny. Whether it's abuse from a mother or a bunch of "mean girls" growing up, some women for whatever reason believe what the manosphere says about them, and insist it must be true for all women, everywhere. It's a pity, and I can spare some sympathy for them...but not all that much. At some point any person who's been abused as a child, male or female, has to decide to either rise above that abuse or allow it to define them. The self-loathing women of the manosphere, much like its other residents--MGTOWs abused or raped by female caretakers, or their distaff counterparts, like radfems abused by their fathers--have chosen the latter.
The second reason, however, is far more calculated. Frankly, I'm torn between admiring its cunning and detesting its immorality and lack of dignity. It is exploiting the simple fact that most, if not all, manospambots are thirsty fools who'll mindlessly embrace any women who mouths the platitudes they want to hear...which makes them a nearly limitless source of both validation and cold, hard cash for any women willing to tell them that women suck. Wallen probably gets off on the laughably effusive praise showered on her by the simps (a favorite manospambot term--ironic they use it on others when it describes them much better) at AVFM. They hail her as some unparalleled sage when all she does is repackage the same tired misogynist bromides that were already old when her sisters repeated them for the ten thousandth time. If I were an attention whore, I could get as much of it as I could possibly want by baiting these rejects and giving them a tiny sliver of the validation they so desperately crave. The return on investment is truly impressive. A handful of crappy blog entries on a semi-regular basis and you'll get a legion of slavering fanboys bearing single-minded devotion usually found only amongst the thralls of famous actors or billion-subscriber Youtube personalities.
It's also quite easy to make money doing that. Women like Karen Straughan and "Dr." Helen pretty much support themselves through those means. It's astonishing just how many paypal donations you can get, or how many morons are willing to buy your laughably stupid books, if you happen to be a female who strokes their egos and reassures them that yes, women really ARE bad and useless and terrible, and you should never listen to any woman...except, of course, the woman talking to you right now, whose overpriced and under-researched drek you should shell out all your money for.
These gals certainly provide a good deal of laughter, though given the reasons described above, only some of it seems at their expense; the bulk of it at the expense of the larger manosphere which enables them.
