What officially "killed" video rental stores?

The internet killed video rental stores. Mostly streaming sites, but also netflix (back when netflix mailed you dvds).

What about Redbox?

I don't believe that Redbox had very much of an impact compared to netflix and streaming.

Let me get this straight-

VCRs and VHS are no longer being produced, but the few remaining video rental stores left in the U.S. and presumably in other parts of the world carry VHS and DVDs and Blu-Rays for rental.

The internet as you said, "killed" video rental stores. People were uploading full movies on video sharing sites like YouTube, Dailymotion and Metacafe, long before streaming services came along, and before DVD rental-by-mail companies like Netflix came along, and before we had DVD rental kiosks like the ones Redbox makes.

Correct?

Netflix was around in the late '90s. How come it didn't affect the video rental store industry back then?

How could Netflix affect the video rental store industry back then? People were still renting VHS tapes from video stores back in the late '90s.

They didn't have smartphones then.

Streaming services and video on demand killed physical video rental stores.

Netflix introduced its streaming service in 2007, just as online video sites like YouTube was taking off.
https://www.nytimes.com/2007/01/16/technology/16netflix.html

What didn't help matters is that Blockbuster did not believe Netflix and Redbox were threats to the company until it was too late to alter their business plans. Its late fees, while being profitable for the company, were hated by customers. As Netflix had no late fees, it became a more appealing choice.
https://www.forbes.com/sites/gregsatell/2014/09/05/a-look-back-at-why-blockbuster-really-failed-and-why-it-didnt-have-to/#1883b3c81d64

As broadband speeds got better and allowed HD video, people moved towards using digital services.

That's what I getting at- "video on demand". How are video on demand services different from streaming services?

Streaming services: Pay a monthly or yearly subscription to have instant access to hundreds of videos. These services offer original shows and movies as well.
Examples: Netflix, Hulu, Disney+, Amazon Prime

Video on Demand: essentially a digital only video rental store. Pay per video, to watch something for 24/48 hours, or pay a higher price to have unlimited access to a film or tv show.
Examples: Vudu, Amazon Video, Google Play.

Most Video on Demand services offers some streaming videos for free, usually with ad breaks.

Good grief!
Netflix wasn't a streaming service back then. Streaming services only became popular/mainstream when broadband became a greater national force (read more accessible nationwide).

What makes you think that Netflix when it was a DVD mailing service DIDN'T EFFECT (not affect) the major video rental brick and mortar chains?

Video rental stores still exist (but not nationwide) and have a hold in areas where broadband internet is not strong or existing at all.

What was Netflix in the '90s before it was a streaming service?

According to the Wikipedia page for Netflix, it was founded in 1997 and was strictly a rental by mail movie service.

They moved to a monthly subscription model in 2000.