Well, people claim to be Satoshi Nakamoto because they want the advantage of the popularity of Satoshi Nakamoto. Take Craig for example, There are still a lot of people who believe that he is the real Satoshi Nakamoto. At this moment, If Craig announces that he is going to create another crypto. For example, Bitcoin lite. There are a lot of people who are going to invest in that shitty project. That's how Bitcoin Cash and BSV have been created. The only thing is, they want to take advantage of the popularity of Satoshi Nakamoto. Most of their target/aim is to scam people. I am not sure if there is another thing behind claiming to be Satoshi Nakamoto.
If somebody is really Satoshi he can very easily prove that by moving bitcoins from famous Satoshi Wallet. Nobody till date is able to do that. Its our responsibility that we must not give any attention to such Faketoshis who can't prove themselves as satoshis.
As you said BSV and bitcoin cash are created by people who are just scammers and its us who fell victim to them just because of our own negligence.