The neighborhoods they built that stuff in (mostly South Lake Union and Denny Triangle) used to be so sleepy in 2010 and earlier. It was a big transformation.
Earlier than that, they were actively dangerous. I spent a lot of my childhood in Belltown, and it was not a safe place in the late 80s and early 90s.
SLU and Denny Triangle are amazing now. Those are some of the few places with restaurants open into the evenings. Amazon, like them or not, does a great job prioritizing local businesses in the retail spaces in their buildings. They can't all survive, but they've had a good track record.
I haven't lived in Seattle since 2011. I remember Belltown having one or two blocks that felt a little spotty or like you wanted your guard up, but the rest of it was thoroughly gentrified by the time I left, and it was a common choice to live for new college grads from the suburbs arriving to work in tech. I have to assume the process has continued.
The area around 3rd and Blanchard is sketchy, but in the rest of Belltown the biggest hazards are incompetent Uber/lyft/doordash/etc. drivers and drunk people on lyme scooters.
