Yes it is easy to copy and change Bitcoin open source code to make new coin but it is very difficult to create successful fork. And Litecoin was made by changing Bitcoin code but it is not true fork like Bitcoin Cash which split from main network. Main reason most forks fail is that they can not get support of miners and developers and users. As you correctly pointed out successful fork requires huge amount of power and money and influence. This shows that true value of cryptocurrency comes from community that supports it not just from code itself.