The government have trotted out concerns about fans congregating in pubs before and after games as a reason, but you're not telling me none of those punters at the Palladium went for a drink or a meal before the theatre. Individual licensees have responsibility to ensure their premises are compliant in the West End just as they are anywhere else in the country. Equally, stadium concourse bars and food outlets as well as toilets would be potential pinch points, but no more so than in a theatre where they face the same challenges of getting a number of people fed and watered during a relatively short time window. Much has been made of the reduced transmission risk outdoors compared to indoors, so it really begs the question why theatres get the green light first.
I think the idea of allowing fans to watch games on big screens indoors at grounds with the curtains shut so they can't actually watch first hand is designed to highlight the absurdity of the current rules as much as it is to do with bringing in a little bit of additional revenue.