It was just a needlessly disruptive move to cynically try to get an audience that would never be able to use their new services onto a new platform.

Someone using Teletext in 2018 was not going to be able to navigate the world of BBCs internet connected TV applications.

It was a decision entirely driven by "Sign In" metrics (that's still in place). It's a prime example of Goodhart's Law, which apparently no product owner in the BBC has ever heard of.