Why apt package chromium-browser installs snap package instead?

For Ubuntu 19.10 it was a developer's decision. See cite from release notes:

Ubuntu 19.10 New Features

The Chromium browser is only available as a snap in 19.10. This blog post has more details.

It is normal and expected.

If you don't want to install the Chromium snap package, see How to install Chromium without snap?

I had the same problem. I disabled/removed snap/snapd from my Ubuntu and didn't want to install it again because of Chromium. Since Ubuntu and Debian are usually compatible, I installed Chromium from the Debian repositories: https://askubuntu.com/a/1206153/1038363

I've had the same problem. Wanted Chromium, but no via Snap. Found Chromium Dev PPA, works stable so far: https://launchpad.net/~saiarcot895/+archive/ubuntu/chromium-dev