I think that Ladybird's success has more to do with the fact that kling is one of the few people who knows how to write the whole browser than with marketing. But yeah, kling is also a great communicator.
SerenityOS was already quite successful before they started Ladybird. So successful that he was already making enough off sponsorship to do it full time. It was having the time to take on something as ambitious as a full web browser for SerenityOS that led to the project to begin with.
I agree that Ladybird is lucky to have a dev not only of his seniority but of his specific expertise. However, there is no denying that a huge reason for the success of his projects is non-technical and more about his ability to build community and engagement.
