PetaPixel explains why Sigma has to make an APS-C L-mount camera:
For starters, Sigma now has a lovely line of mirrorless APS-C lenses that cover a pretty fantastic range. But perhaps more important is that L-mount has not seen an APS-C camera in quite some time. The last one was the Leica CL from 2017. Either Sigma thinks there’s an existing market for APS-C lenses in L-Mount — I don’t know what that market is — or it thinks there will be a market. I’m inclined to think the latter.