To be pedantic - mainnet Ethereum didn't 'roll-back' those hack transactions either. They are still there on etherscan if you want to look for them. The DAO hard fork introduced an unsigned transaction that moved the hacker's funds to a refund to a refund contract.
I found about this fairly recently. You seem knowledgeable about the topic. Can I ask you how did the community react to this/what do they think of this episode today? Because having full control over the coins is one of the big reasons why proponents are against regular banks and state-issued currency, yet here there was a clear breach of that control.
The developers don't have full control like that. They were only able to execute TheDAO hard fork because the community was very small at the time and was reasonably united behind the developers in carrying it out. It was something of a unicorn of circumstances that it was even possible because the funds were still locked up for a period of time and the hacker couldn't sell them, which meant there was only a single loser in the fork (the hacker), and a large community of winners or people who weren't directly effected either way. I personally think the refund stage of things should not have happened and the funds should have been burned instead, simply as a means to make sure the investors learned that risks of interacting with ethereum contracts were still very real. But that said I wasn't involved in crypto at all then, so, what do I know...
There was a huge debate over it, and in the end everybody got to run whichever version of the protocol they preferred. Both chains still exist today, but most of the ecosystem went with the one that made the change, so that one accumulated a lot more value.
