Danger Supporters Supporting?

The 'experiments' evaluating allowing supporters into/near major sporting events, in the UK, seem to have some glitches. It appears that almost 2,000 of Scotland's new infections with the delta variant of Covid19, can be linked to people who travelled to London to support their country, playing England in the UEFA competition (https://www.bbc.co.uk/news/uk-scotland-57667163). Admittedly, not all these individuals actually had tickets for Wembley stadium. They did, however, congregate around the stadium in large singing and chanting groups. Naturally, there are now concerns about the increased crowd capacities scheduled for the semi-finals and finals, also scheduled for Wembley. Supporters operating in fan-zones near big outside screens, also often appear very clumped and generally unmasked. The Wimbledon tennis championships is another event, where allowing spectators is being trialled. A son, who recently attended, tells me that, although spectator capacity was reduced, this was not done in a very effective way. Spectators for popular games were crowded around the court, close to the action. The reduced capacity was achieved, by leaving the seats in the 'gods' (those highest in the stands, far from the playing surface) empty. We appear to have some way to go, before mass participation events can be held with acceptable levels of risk.