I think there are just fewer people active on these platforms, which isn't great for interaction.
As for v.basspistol.org, that's not a Mastodon instance but a Peertube (derived) instance. Both are part of the so-called Fediverse, but Mastodon (and similar) intent to replace/extend Twitter/Facebook whereas Peertube intends to replace/extend Youtube.
Edit: perhaps worth mentioning is that both types of social media share a protocol called ActivityPub. This is how several social media systems (Twitter replacements, Reddit replacements, Youtube replacements, etc.) can all communicate with each other. NextCloud, for instance, also has an ActivityPub system integrated, which means your toots and the shared files/comments may end up in the same system, all with some manner of interoperability.