4chan lacks any kind of organization whatsoever. It's hard to say that 4chan is any particular thing because it's so amorphous and liable to switch to something else new. That makes it hard for most people to see them as potentially dangerous.
Their posting style also helps. They talk about absurd things, in absurd ways. They look insane, they don't even try to make things reasonable. That makes many people underestimate them, because they seem far too loony to do anything significant. It also makes deplatforming them unappealing. Where are these people going to go if 4chan stops existing? No one wants to see this on their Facebook feed.
In short, 4chan acts like they're too incompetent to do anything.
Parler is full of people who are coherent enough to actually stage some kind of a violent, semi-coordinated attack.
Their posting style also helps. They talk about absurd things, in absurd ways. They look insane, they don't even try to make things reasonable. That makes many people underestimate them, because they seem far too loony to do anything significant. It also makes deplatforming them unappealing. Where are these people going to go if 4chan stops existing? No one wants to see this on their Facebook feed.
In short, 4chan acts like they're too incompetent to do anything.
Parler is full of people who are coherent enough to actually stage some kind of a violent, semi-coordinated attack.