I can shed some light on the btc and bch debate, hopefully without much bias.
Back in the day, btc was getting popular, and people in the know started to get worried that the 1Mb block size limit may end up causing problems down the road. Well this limit did in the end cause problems. These problems took the shape of higher transaction fees.
Because the fees are set by market forces, and with the 1Mb hard size cap, well market forces solved the problem by ratcheting up the transaction fee. And so they went through the roof. This hurt Bitcoin reputationally quite bad. You still hear this argument being used by those interested in trashing cryptocurrencies.
Since btc was run by nobody really, but there were some key players, many ideas were discussed but a consensus on what to do remained elusive. A lot of passions were inflamed and discussions became acrimonious.
Then comes the most simple a logical solution, increase the block size. Make the 1Mb blocks 4Mb, or 8Mb.
It is not that the core developers of btc had not thought of this. They just did not like this solution. Mainly because I believe it seemed to them to be an irresponsible solution. It would solve the problem short term, simply to make a larger headache down the road.
It must be remembered that to run a miner or a full node, then a full copy of the blockchain must be downloaded and maintained. Going from 1Mb to 2Mb would double the size of the bitcoin blockchain.
Bitcoin Cash was forked from Bitcoin in probably the most well known hard fork in cryptocurrency history. It is still the most valuable bitcoin forks there is.
This fork was stupidly easy! Take the code of the bitcoin miner and change the parameter of the blocksize to whatever you want and release it. The hard part is getting others to follow you and run your version of the miner or node, to build that community that makes cryptos work. Well BCH got a few bitcoin whales behind it and off they went.
The rest is history.
just to add a fact: when a blockchain is hard forked as in this case, if you held btc before the fork, after the fork you have your btc and you have the equivalent bch as well. If fact they are held in the same wallet address. Everything is essentially mirrored.
This gave rise to the replay attacks, which I will not explain here, but if you wrap your head around all this, then do a search for replay attacks and they should make sense to you.
Hope that was impartial.
If I got some facts wrong, I humbly invite corrections in this thread.
p.s. I am a bitcoin guy, I sold all my bch soon after the fork. I got nothing against the the tech really, it is the personalities behind bch I object to. The way they have behaved, and their selfish self declared goal of supplanting bitcoin. That I cannot abide.