I think it was Dave Clark's vanity. Some kids just assumed "Dave Clark" would be the guy singing and the more live shows they did, the more evident it was that Mike was what drove the songs. And that Clark wasn't that impressive of a drummer. And, that dense, tight sound on the records was probably super hard to replicate with the venue sound systems they had then. Clark knew he knew how to generate a really good hit recording - that was his strength so he worked that. Clark was a businessman first. He could be off making more money, cutting deals on all his side projects, and on cutting his bandmates out of all the money. Like James Brown, Clark thought he was some amazing entrepreneur, with barber shops and restaurants and you name it. I think the enterprise wrapped up the way it did, because the other guys realized they were toiling for not much gain. Finally, DC5 was aimed at a slightly older demographic than the Beatles, one for whom The Pill arrived 2 years too late. Beatles fans remained single, while DC5 fans started families or got drafted, etc. Which of those 2 demographics would continue to buy records?