Because it's easier to punch down than it is to punch up.
I live in a liberal state and I think I run into transpeople once in a blue moon. Sure there are gay people but most of them keep to themselves. I do agree with the idea that these ideas should not be pushed on to children and that you need a certain level of maturity to explore one's sexuality and gender identity if that individual even finds it necessary. I think the powers that be use LGBTQ with Black to an extent as a distraction and I also think some Black women weaponize it to an extent as a means of undermining Black male patriarchy.
BUT
White supremacy is a much larger and more difficult fight because it affects us on 3 levels. As an immediate threat to our physical safety with race soldiers, police, shooters etc. On an economic level with lack of access to capital, higher interest rates, lack of access to jobs with comparable qualifications, insurance costs, etc and just the emotional toll with an undermining of Black beauty, black masculinity, portrayals in the media, news etc. Low key many of us still seek a level of approval from whites, hell some of us seek to start families with white people as a means of giving our offspring a chance to integrate into their communities.