I'll start off by saying, obviously my numbers are exaggerated at a macro level, but might be the case for individual contractions in the demand for trainees.
Of course, it's partly due to TCs increasing up until 2024, it's a contraction/correction rather than necessarily being a decrease (only around 8% since 2024). Finance is another field lowering graduate intake (although more aggressively than law).
I do worry though this trend is more than a correction. The benefit of commercial law, is companies will need advice both during economic boom and recession (which is part of the 'stability ' of the profession), however the demand for legal services is not extremely elastic. If AI does make the job more efficient, it may not replace lawyers as such, but it might reduce the hiring rate (as with any field), and I do wonder if the contraction is partly due to this implementation.
Maybe I'm just worrying too much / too paranoid.