Why does one flight change wreck the whole trip?

You can book a flight. That is not the hard part. The hard part is the moment a gate agent tells you the flight is cancelled and three people are texting you at once, each wanting a different answer. That panic is not a sign you are bad at travel. It is a sign your team never agreed, ahead of time, on what matters most and who decides. So every change becomes a group debate, starting from zero, while a clock runs. You do not need to become a travel expert. You need a plan your team built together, before the trip, for what happens when the plan breaks.