I genuinely believe that any human getting enough power (e.g. by moving up in a big company) tends to become a toxic asshole (without even noticing themselves). So that's one explanation.

On top of that, I believe that the sum of the actions of well-meaning people doesn't always result in something good. In big companies like Google, I'm sure that many people are taking decisions that they think are well-meaning, but the result is that Google is a toxic entity.

In other words, because Google sucks doesn't mean that all Google employees are evil. Many of them just take their high salary and try to do well, conveniently ignoring that they contribute to a toxic entity.