I think sandboxes are having their moment because it's become undeniable that coding agents are useful, and that they're more useful if you run them in YOLO mode rather than having to approve everything they want to do.

Coding agents are still a relatively new category to most people. Claude Code dates back to February last year, and it took a while for the general engineering public to understand why that format - coding LLMs that can execute and iterate on the code they are writing - was such a big deal.

As a result the demand for good sandboxing options is skyrocketing.

It also takes a while for new solutions to spin up - if someone realized sandboxes were a good commercial idea back in September last year the products they built may only just be ready for people to start trying out today.