Number of participants isn't really the best gauge when we're talking about stadia. Basketball might be played in most British schools and casually by many more people in yards with a hoop, but few British people could name a single UK basketball team; our basketball league is essentially ignored by mainstream media. Rugby takes a lot more organization due to being an inherently dangerous sport especially without competent technique and refereeing, but international games see sellout crowds of 80,000 with millions more watching on TV.