Some chameleons can and do get along with each other, it's just not the norm. So some people (people with lots of chameleon experience, who can spot the signs of stress or discontent a mile away) can and do successfully keep a number of chameleons together in a freerange setting, provided they have plenty of space and the option to separate themselves from the others if they want to.
I actually kept 4 male panthers together in a room free range for a year and they did beautifully. Most of them were young when I started so they essentially grew up in this setting and did really well. And it was facinating to see how they communicated with each other, negotiated things, and sorted out their own issues just by gesturing. I was lucky all four were not particularly dominant personalities.
And then species like Meller's, for example, can sometimes be fairly communal. Although again, with varying personlities not everyone is going to click with each other. But that's why you'll see groups of Meller's chameleons more often, for example.
And as a fun fact, I've found males to be generally much more tolerant of each other than females. The girls tend to have a lot more fury against anyone they don't care for!
But like I said, no one should try this without a lot of eperience and a lot of caution. There's more that goes into it than just putting two animals together on a free range.