This entire article is about Why. Read the "An attack on SHA-1 feels plenty viable to me" section for the most info.
I see -- it's not announcing any news, or any new theories; it's just a roundup of last week's news.
Yes. Much like last week's news was. :-)
It's a roundup of last week's news, and (hopefully) better all-around explanation and background for people with less technical knowledge. It also points people to another tool I made, https://shaaaaaaaaaaaaa.com, to actually do the SHA-1 check.