I think this is honestly less about the notoriety of .com, and more about the lack of affordable and available domains for startups to purchase. Got a five letter named startup? That’ll cost you tens of thousands of dollars, IF you can even get it. Meanwhile there’s hundreds of gTLDs that you can buy a domain on for $10-$30/yr.
There’s still stuff available for reasonable prices but it’s just a lot of work so it’s easier to get some random tld.