Here's a longer excerpt of the first part of Sermon on the Mount. The thrust of the lesson, as I take it, is that spiritual comfort is for all no matter how meek. Indeed, the meek will actually inherit the earth.
All lives mattered to Jesus, of course. All lives matter to those who say "black lives matter" as well, believe it or not. But in Jesus's society as well as ours, all are not equal. The disadvantaged need to hear that their lives matter, too.
Just look at his life. Jesus consistently sided with and comforted the poor, the hungry, the sick, the old, women, prostitutes, etc. Those disadvantaged by the social structures of the day.
Jesus also had a consistent message against the concept of hoarding wealth: see the camel passing through the eye of the needle verse. https://www.biblehub.com/matthew/19-24.htm
To Jesus, all lives are equal, which implies a process of equalizing.