This is not true. The Democratic party has become the party of the ultra-wealthy. Except for Elon Musk and Peter Thiel, how many tech billionaires are Republicans?
Besides, many of these Harris voters do have assets, but they think they're safe because the threshold for this tax would be $100 million. They think their 401k is safe. They're wrong. No tax ever begins by falling on everyone, but eventually, everyone will pay it.
Their stance on this issue (and "tax the rich" more generally) is that they're fundamentallu incapable of conceptualizing second-order effects for any decision.