Corruption is a broad term, it has eaten deep into many spheres and aspects including sports unfortunately. It has many applications. I remember a story of how a friend who is a good athlete told about he and three others participated in a federal government 4x100 athletic competition, they came first at the end and were issued an equivalent of $2 to share as their price money.
It sounded very ridiculous for the government to issue such an amount, i am very certain that the officials involved has pinched out percentages from the money, and unfortunately, that was what was left. This is also corruption.
It's not broad term, any kind of abuse in power is already a corruption, it's not a broad term but it's more like it can define a lot of activities rather than the other way around. You're friends, I feel bad for what they've experienced but they could've been able to appeal it if there's a rule book that states their prizes when they win.
Agreed, anyone that is at the top of a hierarchy and then decides to take decisions that he knows are going to benefit himself is committing an act of corruption, but there are some countries where this is so common that it also gets to the sport world.
For example it is very common in many countries that soccer players actually need to pay money to move up the ladder and become professional, this does not make sense, as a young and good player should be given priority as not only will benefit the team and they could sell his rights for a high price, but those dealing with those players do not care about it and are only looking for their own personal benefit.