The problem is that most of what was done in Panama was legal. They were avoiding taxes, not evading taxes.
If they were breaking the law, they could be hauled into court. But, if they're following the law, but using loopholes which should be illegal, then the only solution is to close those loopholes.
Then it's a case of millions of people who care just a little bit about having these loopholes closed, but have other priorities like gun violence, global warming, abortion rights, government spying, affordable groceries, not to mention their jobs, their families, their kids, etc. On the other side, there are a few dozen lawyers and lobbyists who are paid to make keeping those loopholes open, or opening new ones their #1 priority for a minimum of 8 hours a day every day. It's no surprise that the side with money wins this one.