If their evaluation criteria is good, they could get away with 0 cost to build the best possible system (motivated by competition on a market).
Actually, I think it's almost entirely the same problem as fake accounts, from Twitter's perspective at least. It's all a measure of usage and demand by customers, and when people are used and investing/involved/compensated for that fake increase, any major drop rocks the boat.
Of course, the fact doing it too well hurts the stats doesn't help either.
I disagree. At least it shouldn't be that hard for a company with Twitter's level of engineering and data science sophistication, and yes, I do realize that most of their best technical talent is long gone.
While nothing is a panacea, there’s little evidence that Twitter is doing even the bare minimum.
But no, Twitter had to "take matters in its own hands" and "control the ecosystem". Much good that brought.