Gender and sexuality have been fluid for as long as we've recorded them. It's in all the primary sources.
Trans people (and gay people, and bi, and asexual..) exist and have always existed - it's only now that modern medicine is capable of and permitted to let them shape their body in the way that matches their identity. It also happens to be during a resurgence in anti-LGBT rhetoric that's part of the MAGA "we had it right in the '50s" dog whistle. Their activism is a natural result.
Trans people (and gay people, and bi, and asexual..) exist and have always existed - it's only now that modern medicine is capable of and permitted to let them shape their body in the way that matches their identity. It also happens to be during a resurgence in anti-LGBT rhetoric that's part of the MAGA "we had it right in the '50s" dog whistle. Their activism is a natural result.