Ogg Vorbis was a novelty at best, and it was the only decently widely adopted open source competitor for any of the items listed that was available at the time.
HTML5 was only just published when Chrome launched. So Flash was at that point the only option available to show a video in the browser (sure, downloading a RealPlayer file was always an option, but it was clunky, creators didn't like people being able to save stuff locally, and was also not open source). Chrome in fact arguably accelerated the process of getting web video open sourced: Google bought On2 in 2010 to get the rights to VP8 (the only decent H.264 competitor available at that point) so they could immediately open source it. The plan was in fact to remove H.264 from Chrome entirely once VP8/VP9 adoption ramped up[1], but that didn’t end up happening.
Flash was integrated into Chrome because people were going to use it anyway, and having Google distribute it at least let them both sandbox it and roll out automatic updates (a massive vector for malware at the time was ads pretending to be Flash updates, which worked because people were just that used to constant Flash security patches, most of which required a full reboot to apply; Chrome fixed both of those issues). Apple are the ones who ultimately dealt the death blow to Flash, and it was really just because Adobe could not optimize it for phone CPUs no matter what they tried (even the few Android releases of Flash that we got were practically unusable). That also further accelerated the adoption of open source HTML5 technologies.
PDF is an open source format, and has been since 2008. While I don't know if pressure from Google is what did it, that wouldn’t surprise me. Regardless, the Chrome PDF reader, PDFium, is open source[2] and Mozilla's equivalent project from 2011, PDF.js, is also open source.[3] Both of these projects replaced the distinctly closed source Adobe Reader plugin that was formerly mandatory for viewing PDFs in the browser.
Chrome is directly responsible for eliminating a lot of proprietary software from mainstream use and replacing it with high-quality open source tools. While they've caused problems in other areas of browser development that are worthy of criticism, Chrome's track record when it comes to open sourcing their tech has been very good.
[1]: https://blog.chromium.org/2011/01/html-video-codec-support-i...
This is what PDF.js is...
> PDF.js is built into version 19+ of Firefox.