Ethereum did not intentionally split. Vitalik and his chronies intentionally hard forked, but they assumed that by having the support of the major mining pool administrators and client/wallet developers (IOW, a dozen or two people), that the original chain would just die. But of course it didn't. Users remained, speculators speculated, miners returned to the original chain. It was not intentional. That's why the Ethereum Foundation told exchanges to ignore the original chain and ignore replay attacks. They planned on the original chain just dying. Silly, especially in a case where the hard fork rewrites history.
put it this way. if ethereum just done a roll back.. the 'hacked' ether transactions would have got orphaned and everyone would make new blocks ontop of the backdated chain
but instead vatelik actually added a bit more code to intentionally black list nodes against each other to cause a split (controversial fork)
--oppose-dao-fork
that oppose dao fork. is the flag to cause an intentional split by bypassing the standard orphaning mechanism by not letting the nodes talk to each other to come to a consensus.
so ethereum was an intentional split. rather then changing the rules for everyone to head in a single direction and let orphans take care of the minorty.