Those are job postings at the for-profit Mozilla Corporation, the layoffs happened at the non-profit Mozilla Foundation.

They're theoretically connected, in that the Corporation is a subsidiary of the Foundation, but to my knowledge, they practically don't hand money from the Foundation to the Corporation, because the Corporation has magnitudes more money anyways.

Layoffs sometimes mean freeing up salaries for different positions (e.g. a company pivoting). Curious jobs though, not really sure what to read from those tea leaves....