They tried to realign package management with web standards and tools that browsers can share (URLs and importmaps and "cache, don't install"). They didn't offer compatibility with existing package managers (notably and notoriously npm) until late in that game and took multiple swings at URL-based package repositories (deno.land/x/ and JSR), with JSR eventually realizing it needed stronger npm compatibility.

Bun did prioritize npm compatibility earlier.

Today though there seems to be a lot of parity, and I think things like JSR and strong importmaps support start to weigh in Deno's favor.