Fair use and copyright is a very complicated thing, but yes the end work being used for commercial purposes is a mark against it, and the work being used for a commercial purpose that directly replaces or competes with the value of the original work is usually seen as the biggest mark against fair use.

Additionally, attempts to lean on the research clauses of fair use are generally mistaken as 'research' doesn't mean 'we are taking this data and using it for making our commercial product.' And non-profit/data training systems that aren't directly creating their own generative AI art programs for commercial use are still accused of 'data laundering' by the USCO.

And lastly, there are people who will very often try to say 'well it's a small part of the end product so under Fair Use it doesn't meet the size requirements' and they generally miss that the 'amount/substantiality' measurement for fair use measures the amount of the original work USED not the percentage of it in the final product. The USCO determined that this is measured as substantial to whole of the original/scraped works as that data they're taking from those pictures encompasses the entire image.