Fundraisers and charities, when you have a lot money, are rarely acts of charity. They tend to be PR campaigns and power plays.
Honestly, even when the acts have good intentions, they are often quite damaging. The involvement of the wealthy in charity is very similar to their involvement in politics. Their wealth buys influence and gives them a disproportionate say that allows them to ignore and overrule the will of the people and sometimes even reality.
For example, look into the impact of Bill Gates's "acts of charity" in the education space. He poured money into charter programs that negatively impacted public education. Later studies showed that his programs were not particularly effective.
Let's say, hypothetically, that a very rich person is convinced by some charlatan that they found the a means to produce free energy. The wealthy person throws tons of money at the idea. How many talented people will be taken from other legit programs because the paycheck at Bullshit Energy Nonprofit is better? These rich people are successful and think they know bestr. Their money ensures they get treated like experts because money makes things happen whether or not those things are helpful.
You don't even need bribery. You can just throw money at something and make things happen.
If you think something is true, you can pay the world to prioritize things as if it were true.
If you think vaccines cause autism and you are rich, you can create massive "education" campaigns and the like to convince people its true. You can buy ads telling people its true. You can amass an enormous following of people who believe you and change policy without bribery.