The Cheltenham Festival and the football matches you mention should never have gone ahead. However, like all the information we get today, the figures that the NHS data analysts have "calculated" should not be taken as concrete. There was no lockdown at the time. What if the hundreds of thousands of spectators involved had spread around the country, going about their normal business? Would the infections and deaths have been higher/lower/the same? Who knows? It's a bit bold to state categorically that these events cost over a hundred lives and 17,000 infections.
Incidentally, my wife and I had our first jabs yesterday. I certainly didn't feel great today but my wife had nausea, headaches, exhaustion and kept going back to bed. (This is unheard of from my good lady who regards any form of feeling unwell as an insult). I trust it will be worthwhile in the end!