Your conflating fees charged to Merchants (by processors) and rewards offered to Card Holders (by issuers).
While often the same bank performs, or is a partial owner involved in, both processing and issuing, the percentages you quote are largely disjoint.
> I'm reading that Visa typically charges 2.3% to merchants ...
The Discount Rate[0] a Merchant pays varies significantly based on the line-of-business, charge-backs, processing contract, and a bunch of other things.
> ... at least on average 1% of each transaction goes to cardholder bonuses ...
Again, issuer costs have no bearing on Merchant fees nor the profitability of processors.
0 - https://www.creditcards.com/credit-card-news/glossary/term-d...