If a user used Stripe "the chance that a visitor would abandon their donation at the Checkout step halved from 22% to 10%"
While that's an interesting data point, plausible explanations could be anything from very positive, such as
(a) Stripe's Checkout process being dramatically more effective for signed-in users, for example because of the reduced effort required to complete the transaction
to very negative, such as
(b) Stripe's Checkout process causing a horrible drop in conversions for users who aren't signed in, for example because of the added complexity that comes from their "remember me" mechanism or the unfamiliar branding.
It doesn't seem at all surprising that previous Stripe users would convert better with either of these relatively extreme explanations -- either those people had an easier interface to use, or they were necessarily already familiar with the Stripe brand.
While that's an interesting data point, plausible explanations could be anything from very positive, such as
(a) Stripe's Checkout process being dramatically more effective for signed-in users, for example because of the reduced effort required to complete the transaction
to very negative, such as
(b) Stripe's Checkout process causing a horrible drop in conversions for users who aren't signed in, for example because of the added complexity that comes from their "remember me" mechanism or the unfamiliar branding.
It doesn't seem at all surprising that previous Stripe users would convert better with either of these relatively extreme explanations -- either those people had an easier interface to use, or they were necessarily already familiar with the Stripe brand.