You did everything correctly, however it seems you don't realize how distinct audio tracks work. You can switch between tracks in your media player. Every media player will play one track only, never mix multiple tracks. To get a mix of both tracks, you need to mix them with some audio postprocessing software like Audacity and replace the two tracks with the mixed track. This is the purpose of multiple audio track recording in the first place: to process and mix them in a postprocessing step.
If you want a mixed track by OBS and at the same time 2 distinct audio tracks for your 2 sources for possible postprocessing, add a 3rd track in OBS and check both audio sources for this track. Use track 1 for this mixed track, since media players usually play track 1 as preference at startup.