Donations from individuals are capped at $5,800, so whatever money Carrick is getting is not one giant gift from Sam Bankman-Fried, but rather many small ones from individual Americans.
There's a really easy way around the $5800 limitation, called a super PAC (Political Action Committee). Super PACs don't give to campaigns directly, but try to influence races via ads, etc. There are no restrictions on super PAC funds.
In this case the Protect Our Future (super) PAC (https://www.politico.com/news/2022/04/19/crypto-super-pac-campaign-finance-00026146). I'm not clear exactly how much POF spent on the Flynn campaign, but SBF donated $13M to POF.