Correct me if im wrong but if there was a handful of compuers running the mining software then life would all carry on as normal.
Yes. That was actually the vision at first. People that will help to extend the chain and outpace any attackers with their CPUs. Couple of years later, we had GPUs and even stronger machines like ASICs. In a way, Bitcoin on its early years had better hash rate distribution, which means that it had better decentralization.
btc is like the internet, you take a big chunk out and it carries on as normal.
I don't get how people equate Bitcoin with the internet. They aren't the same. Not all people have the same rights upon internet, in contract with Bitcoin.
Are bitmain, antminer and all the big mining firms and pools leeches on the system?
That's a great question.
Well, you have to understand that nowadays the thing differs. Back in 2010, I'd guess that the number of working CPUs wasn't even a 4-digit. That being said, if you get rid of the pools, the miners will have to solo-mine,
but only one person would gain the bitcoins. Right now, if you provide your computational power on a pool, you'll be rewarded whether you find a valid hash or not. If you go solo, your chances to be rewarded are tiny and thus, you won't mine, because it won't bring you profit.
On the other hand, gathering all that power in one entity can lead on mining centralization, rather than the “leeching” you're referring.