Friend of mine is a Chiltern planner. They have several "base" event plans that they manipulate to best suit the day and time of the event. Strengthening occurs where possible, and Wembley is added as an additional stop in all trains after a certain time. Trains are ran later than normal. It is very very wrong to say they make no effort.
You also have the issue where they are told by the organisers what the expected finish time is, so the longest services are slotted in to a time bracket after the event to sop up the majority of the crowd. If it overruns (such as extra time or penalties in the case of football) then a chunk of the strengthened services have gone with no one on them. You then complain it ramped up too early and no one cared to think about what could happen in the game.
If you ran the strengthening plan on the basis of it going to ET and Pens and it doesn't, you've got up to an hour to wait before the full enhanced service kicks in. And you'd then complain about how it didn't start ramping up soon enough.
Of course, all the planning in the world cannot fully mitigate the effects on the service of an incident such as a fatality. And, at the end of the day, if you've got to queue a bit longer than you'd hoped, who cares? Have some empathy for those affected by it more than you.
