Suddenly 99% of the world is no longer discouraged from being fiscally responsible. Do I really care if a billionaire is fiscally irresponsible? Maybe for a single generation. After that, we're good.
What GP proposed was a Wealth Tax which is an additional tax on _living_ people who have a net worth over a certain amount.
What you linked is an Estate Tax (aka death/inheritance tax) which only applies when someone passes wealth on after death. If they decide to give all their money away to charity or otherwise spend it while they're alive it does not apply.
Suddenly 99% of the world is no longer discouraged from being fiscally responsible. Do I really care if a billionaire is fiscally irresponsible? Maybe for a single generation. After that, we're good.