When the baseline of corruption is high enough and those who judge you are equally or more corrupt, convictions for "corruption" are a weapon from those who do not want a specific someone on the government rather than real intention of reducing corruption.

Simplifying, it's like this: If the road to presidency is corrupt, you either become also corrupt (on a varying degree) or stay as one of those parties with no more than 1% of the votes. But then, there's a pact of silence between cronies. And those who are accused of corruption are the ones that either went too far or went against powerful people in the government.

I take all those trials with a grain of salt.