Why I consider that the catch is possible:

In year 2020, US men earned overall (slightly more than) one third over their female counterparts in wage labor, and almost two times more in self-employment. xxxxxxxxxxxxxxx, despite constituting negligibly higher part of the workforce.

The same year "About half of women [said] they out-earn or make the same amount as their husbands or partners, according to a new survey from TD Ameritrade"; various surveys put self-reported estimates of women outearning their husbands anywhere between 21 and 50%. BLS Current Population Survey puts the estimate at 33% including families where husband does not work, and 25% excluding families where husband does not work.

This goes in contrast with what I dug up about, say, France, where female involvement in the workforce is 10% lower, and the data is from 2011, but still: full 21% of couples had unemployed wife, full 20% of couples had wife employed part-time, and even in reported 44% of couples where both partners were employed full-time, men were responsible for 56% of the income, leaving only 15% of couples with any other type of arrangement (i.e. with only female primary breadwinner). xxxxxxxx

It also goes in contrast with various other studies indicating women's attraction to indicators of status and wealth, and female breadwinners being generally a source of higher risk of divorce.

Possible types of catch:

His job offers very generous family health insurance plan and/or other types of free goods and services that are technically not his wages. His job pays entirety of the rent. He's a trust fund child / heir who realistically could never work in his life and still afford decent lifestyle. He is a self-employed private entrepreneur, so technically his wage salary is zero. He is temorarily unemployed due to health problems, after earning more than you for years/decades.

If there is no catch: how long have you been living together?