> Why did companies seek 10x ninja rockstar coders and subject them to leetcode interviews—surely, a junior fresh out of college could churn out something if it's so easy?

Because companies resent that they have to take on risk and pay people to extract value from the market.

Ugh, why do we have to pay people to code, maintenance, etc. Lets pay people to extract more value for our bonuses and shareholders. Lets try to only hire heavyweights so that we don't get hung up on that difficult-to-measure coding process, knowledge transfer, messy human-ness. Oooh how nice, we can hire a fewer employees that know how to leverage code agents that free them up to think about that what REALLY matters...