I'd say most users won't type "mastodon.com" in their "browsers". They will type "mastodon" in their "internet" or, if technically savvy, into Google first. Second, from following the fediverse (not just mastodon, but also pixelfed, peertube etc), i have a feeling that they aren't into mainstream, general audience anyway. A lot of them are small focused instances and as such, won't even be attracting new people via Google, but by invites anyway. Many instances have closed registration anyway. So if you need to land anywhere it's likely not on mastodon.social, but something like ...(checks last five accounts to post directly on top of timeline): icosahedron.website, fostodon.org, mastodon.social, mastodon.technology (my instance) and hackers.town.