I apologize.
Your initial question felt like it was a disingenuous trolling attempt, but I see now that perhaps you are genuinely unaware. Perhaps you joined the whole ecosystem after these events and are playing catch-up?
At the time there were no examples of contentious hard forks from which both sides survived.
Some on the ETH side felt that ETC was an attack on Ethereum by speculators just out to make a quick buck.
And @barrysilbert notoriously tweeted about his ETC support and purchases, leading to his delightful "Barry Shillbert" nickname and further conspiracy theory that ETC was an attack on Ethereum:
@Poloniex is part of the @DCGco portfolio of companies, so of course he engineered all of this, is the devil and his breath smells of sulphur. /s
Indeed, many speculators did jump on this "second bite of the cherry" at the huge gains on ETH.
Incidentally, ETC philosophy is very close to BTC philosophy. Hence the "brotherhood".
It is a decent analogy, though I would disagree that the philosophy is 100% aligned.
Many BTC people are maximalist, and don't believe anything other than BTC works.
Others in BTC while perhaps admiring the ETC DAO fork resistance think Ethereum account model is just a mistake because it does not scale as well as UTXOs (as @mwilcox taught me).
ETC developers are building great tooling now which is actually applicable to ETH as well, and while some mistrust remains between ETH and ETC communities it is very minority. Most people are open to collab.
Yes, there is some "market conflict".
What happens when ETH2 launches?
Will ETH1 continue at that point even if that is some subset of the ETH community "unbombing it"?
If ETH2 and ETC coexist then are those competing or complimentary?
But working together makes sense right now. ETC and ETH1 face the exact same problems. They are close, and getting closer. ETC just hardforked in Byzantium op-codes. Istanbul and Constantinople forks will follow in the next year or so.
It is becoming easier and easier to port apps back and forth. That was true at the time of the fork too, but the conflict made that politically untenable. You would have to leave the "100% ETH" purity pledge gang.
That is happening now.
We are getting more and more developers who are open to ETC support.
One simple reason would be that the network is less congested at the moment, and gas is much cheaper. Save some money. Deploy your dapp on ETC!
We were never just a protest coin.
Expect ETC to become a really serious option for "Ethereum family" deployment in the coming months.
Expect more dapps and more collaborations.
END tweet-storm!