Money and power have always concentrated with the few. People with money and power tend to prefer to associate with people with money and power. Wired magazine recently did an interesting piece about this. So, it shouldn't come as any surprise to anyone that there is collusion amongst these folks.
When us regular folks get together and talk about the world and what can be done to make it a better place, our words are nothing more. However, when rich and powerful people have these talks, sometimes real actions can ensue. Sometimes, these actions may not be strictly legal, but with money and power can come a sense of invulnerability. We call this corruption and it is a lot easier to fall into when you're rich and powerful than one might think. There are so many laws to keep track of.
Thus, when Mr. Trump openly attacks the Bidens for corrupt behavior, he may not be wrong. There are probably a bunch of people out there that don't like any Democrats and are happy to see them get burned, but if you want to be serious about going after corruption, start in your own house, because that's where you gain legitimacy for the cause.
Donald Trump's selective persecution of corrupt behavior can't help but look like a political maneuver designed to help him in the next election. Maybe he feels that corruption is corruption and if its exposure helps him personally, so be it. I know he's not alone if he feels this way. There's a small percentage of the population who love to see him call it out despite the risks to his continued legitimacy as president.
The fact is, corruption is bipartisan. If we want to go after it, we should be just has happy about it when our own party's officials are called out. Corruption isn't a game of Republicans vs Democrats. It's more of a game of Whack-a-Mole. Whenever it pops up, we should uniformly knock it down...but we don't. There is no systematic pursuit of corruption, so we're forced to wait until a political enemy exposes someone. It's a lousy system, but maybe it's better than nothing at all. Or, maybe when exposing corruption becomes its own form of corruption, we should call for a better way. I wish I knew what that was.