Some of the difference in votes vs. personal donations comes from the tax deductible status of donations. Donations to (for example) Arthropoda are only tax-deductible in the USA, meaning that many potential donors living in other countries might donate elsewhere. In a donor lottery this is no longer a concern.
Other factors like currency conversion fees when donating to charities that only take donations in dollars may have similar effects.
Some of the difference in votes vs. personal donations comes from the tax deductible status of donations. Donations to (for example) Arthropoda are only tax-deductible in the USA, meaning that many potential donors living in other countries might donate elsewhere. In a donor lottery this is no longer a concern.
Other factors like currency conversion fees when donating to charities that only take donations in dollars may have similar effects.