i think it’s a combination of two things:

1. these people had an emotional attachment to nintendo and it’s games growing up, or knew someone who did, so thought very highly of it. when faced with the reality that nintendo is just like any other corporation, aka they only care about their profits and nothing else and will act accordingly, the fall from heaven was brutal.
2. the main targets of nintendo’s shittiness are its own customers and fans. microsoft may be helping mass murder of people in Palestine, ubisoft may have protected the sexual abuse of their employees by management, rockstar may do union busting… but gamers are none of these people. gamers are "consumers", and highly lacking in empathy. so, in their eyes, nothing is worse than being "anti-consumer". like, ask any gamer if they like ubisoft and, if not, why. they won’t talk about the sexual abuse, or crunch… they’ll talk about bad overpriced games and microtransactions.