Quick answer
Oppression is often stupidity rather than malice, and the verse says so. The cure it names is not competence but hating gain.
Read both lines
The first line makes a causal claim worth pausing on: the ruler lacks understanding and therefore is a great oppressor. Not cruel, not ambitious, unintelligent about what he is doing, and the damage is the same size either way. That is a real observation about how harm actually gets done from an office.
The second line then names the corrective, and it is not education. It is hating בֶּצַע, unjust gain, the same appetite 1:19 said takes away the life of its owners. The received text carries a variant on whether the phrase is singular or plural, which changes nothing. What the verse implies is that most rulers who oppress are not being paid in cruelty; they are being paid, and a man who cannot be bought is harder to make stupid.
Related: Proverbs 1:19 · Proverbs 29:4 · Proverbs 16:12 · Proverbs 28:2
New King James Version®, Copyright © 1982, Thomas Nelson. All rights reserved. Full copyright information. Scripture provided by API.Bible.
Go Deeper
If this verse has been used to put weight on you that it was never carrying, ask about it directly.