Stripe processes a LOT of money. The customers that get that money need to move it around. Often to banks. Stripe makes no money on that.
Over the last few years, stablecoins have become a preferred means to hold and move money (for convenience, etc).
Stablecoin providers make money on their float -- selling stablecoins means you get free deposits, and risk-free rates are presently around 4%. For every $1M in stablecoins your customers hold, you can make $40k/year. Stablecoin providers like Circle pay about half of that back out to partners that sell the tokens.
Stripe is huge, and well-trusted by customers for handling payments. By adoption stablecoin infrastructure to control financial flows into stablecoins, they can amass huge amounts of stablecoin sales.
If even ~3% of their transaction volume gets held in Stablecoins, and they make 1% a year on that, it's about $1B a year in bottom line.
~$10e9 (daily avg vol) * 365 * 3% (converted to stablecoins) * 1% (net income) = ~$1B