Whether or not you believe in this, it was cited directly in the manifestos of
* the Christchurch NZ shooter (https://www.start.umd.edu/news/new-zealand-terrorists-manife..., 51 dead, 40 injured)
* the El Paso shooter (https://bridge.georgetown.edu/research/the-manifesto-of-the-..., 23 dead, 22 injured)
* the Pittsburgh synagogue shooter (https://www.splcenter.org/hatewatch/2018/10/28/analyzing-ter..., 11 dead, 6 injured)
* the Buffalo shooter (https://ag.ny.gov/sites/default/files/buffaloshooting-online..., 10 dead, 3 injured)
It is why the neonazis that marched in the "Unite the Right" rally in Charlottesville VA 6 years ago chanted "You will not replace us. Jews will not replace us" and "Blood and Soil" (Blut und Boden: https://en.wikipedia.org/wiki/Blood_and_soil)
This is widely known and barely coded language. It is prominently supported and spread by people that X's owner had replied to retweeted previously, and repeatedly. This widely known, widely understood context informs the real meaning of this tweet.