It's fairly unusual for FLOSS projects to register any trademark, and (despite this lack of strict IP protection) it's also very unusual for the owner of a trademark to ask or require a FLOSS project to change their name because it violates a trademark. Not completely unheard of, but still rare.

I don't know why you decided to trademark your project name, but I think the biggest issue here is that trademark law is naturally the domain of IP rightsholders and an outlook that presumes and enforces scarcity when it comes to names, name spaces, and digital content.

There aren't that many reasons why FLOSS projects need to work within that same domain. My thought is that it is better to try and defend the environment of a digital commons that exists outside of them, than to enter into it and try to participate in a quite alien system of existing IP law, which has a lot of presumptions and standards that, as you say, don't really match the world you work within.