According to Lindsay and her defenders, she has been "harassed" for years. Ever since Gamergate, so at least eight years. She even gave a wheezy TED talk about "bad faith" criticisms when she got pushback for her white genocide joke. Why was this "cancelling" the straw that broke the camel's back? Why did she wait NINE MONTHS to quit? As far as I can tell, there's been very little mention of it since the "Mask Off" video. To me, there are two possibilities.
One: she genuinely believes, either consciously or subconsciously, that her lefty critics are right. By her own admission, she gets heaps of scorn from right-wingers, and she just blocks, ignores and dismisses it. Why can't she do that with these woke detractors? Why can't she say to one of her eight employees, "You're now my social media manager, I'm done with it"? Maybe because she wants back in the club. She agrees with these doofuses, so when they call her "bigot", it cuts much deeper than someone calling her "SJW". She keeps searching her name hoping that her station has improved in the wokescold sphere, and it hasn't. And it's driven her insane.
Two: this is all a con. She got a signal boost from her cancelling, but didn't help her book sales. So, she's making a big histrionic show of leaving Youtube, raising her public profile and number of patrons, followed by the glorious return. Even in her farewell screed, she downplays how well her channel is doing, saying it's just "inertia" and "running on fumes." She's hinting that she needs more money. She's begging for support, emotional and financial, and it's working. She got her name into MSM outlets, a wave of twitter sympathy and more subscribers.
I'm leaning more and more toward the second option myself.