Dilma admitted to committing an impeachable offence as specified in the Constitution; if they thought it important enough to include it in the Constitution, the Brazilians themselves obviously felt it was a serious charge. That's the whole point of a constitution.

She has also been charged with forming a criminal organization, of which Temer was accused of being a member. Unfortunately the evidence against him was badly tainted - hopefully they will get him after he leaves office (I'm fairly sure under the constitution you can't be impeached if there are less than 12 months left to run)