Why Does Sweden Have so Many Billionaires?

According to right-wing dogma here in the USA, we have to cut the effective tax rate for billionaires to one far lower than their office employees pay and get rid of most or all of our social safety net in order to protect our poor, beleaguered billionaires from bankruptcy. Perhaps it is so, but if it is, why do the Nordic countries with their high tax rate, a highly progressive one to boot, and with their solid social safety net, produce so many billionaires? Could their ideas work in the USA, or are they just some socialist/communist trick to delude us into bankrupting our terribly threatened billionaires?