https://en.wikipedia.org/wiki/Early_adopter may help for the following.
We in Hacker News are a small percentage of the "Innovators" set. We are not who reddit is wanting to appeal to now.
Reddit started with Innovators like ourselves as a small site and grew to encompass "Early Adopters" from the other Internet communities, it has been growing out and nearly full of "Early Adopters" - it needs to get more people, and to do this it changes the demographic. It needs people like our relatives and co workers who just use Facebook. It needs to grow because more people equal more money. They can and do accept the loss of the original Innovators and some of the Early Adopters as part of the cost to draw in much more revenue.
Thus, removing hateful subreddits, cleaning up the place is part of that. Another is increasing mass market interests - adding celebs and politicians. Another is increasing revenue through sponsored posts, like what Twitter is doing.
Allegedly the reason why this admin was fired was because she was against increasing the amount of corporate sponsored/promoted AMAs, and she was more in favour of community friendly content.