According to the stories, at least in part because of the fact that she raised significantly less money than the other R frontrunners in the race (I still think she would have lost the R contest for the nomination, but I've been wrong about R races before :) ). There *was* a difference between her fundraising totals and those of the others, particularly Steve Gaynor, but it's not what many folks think.
From Yee's report covering 2021 -
From Gaynor's report, of the same period -
The stories like to state that Gaynor is the "money leader," but he's mostly self-funded/trying to buy the job - he injected $5 million of his own money into the campaign.
Given that the job he's seeking would pay ~$380K over 4 years, it seems like a bad investment.
In the interest of being thorough, from Kari Lake's report covering the same period -