For almost all billionaires, that's a far larger constituency and a much more frequent and efficient selection process compared to elections every x years by the 30% of the population who bother to vote. As soon as they stop performing, the money stops rolling in.
"That may seem like a lot of money, but billionaire math can be deceptive. The Sacklers proposed to pay the $4.5 billion out over nine years. Their current fortune is estimated to be at least $11 billion. Conservatively, with interest and investments, this means they can expect a 5 percent annualized rate of return on that fortune. If that’s the case, they’ll be able to pay the fine without even touching their principal. When they’re done paying in 2030, they will probably be richer than they are today."[1]
There are a few cases of powerful politicians serving jail time. I can't think of a single case where a billionaire was put in jail, except for Madoff, because he was stealing from other billionaires. When you've got billions, you have enough to buy politicians every cycle. You are effectively above the law, forever, regardless of how well your initial product line is doing.
[1] https://www.nytimes.com/2021/07/14/opinion/sackler-family-op...
Nearly nobody gives a damn about the behaviour, eccentric, insane, evil, or otherwise, of the primary shareholders of a corporation that is involved, directly or indirectly, in producing products that they consume.
I may think that the Sackler family are murderous scumbags, but if I need medication made by Purdue, that's the medication I'll be buying.
Which means, mostly the millionaires and billionaires. And SuperPACs owned by corporations who have unlimited funds that they can give, because Citizens United showed that $1 = 1 vote.
