I suspect they're doing this because of AI.

Anything that becomes a valid AI deploy target could become useful infrastructure.

The rate of humans testing things in a CodePen will slowly fall off, similar to Stack Overflow.

The rate of AI models deploying to CodePen 2.0 will pick up significantly.

In some number of years, the amount of code written per month by machines will dwarf all code written by humans from 1957 - 2027.

In that world, CodePen 2.0 is valuable. CodePen not so much.