Dwan is something of a reclusive/shady figure these days. Also it's unlikely he's currently playing anywhere close to his skill peak/ the skill level of the four selected - once a poker pro has achieved a level of fame commensurate to his, they can live comfortably for the rest of their days bleeding wealthy amateurs who get their kicks from playing (and losing) high stakes cash games against pros.
Don't know about Blom - probably just insufficient action for him (couldn't tell from the article, but it seems likely they're playing play money cash games, with fixed prizes for players who end ahead).