You see it that way, I don't. The impact of illegal immigrants on African American jobs has been studied as far back as 1992. At the bottom are just four articles from the last 22 years and the fact that most African Americans have achieved middle class or higher economic status, does not detract from the fact that many have not.
You keep using the term "Black" jobs, but I think Trump is referring to jobs held by blacks that are being competed for by illegal immigrants.
He is not referring to the many jobs held by blacks that are not being competed for by illegal immigrants. Trump is not referring to people like my four oldest black grandchildren growing up in the suburbs of Philadelphia in an upper income family all of whom are receiving excellent educations. I do not think they need to worry about illegal immigration personally, but they like you should care about everyone trying to escape poverty and suddenly finding the lower rungs of the economic ladder becoming crowded in the urban areas in which they live.
People like my grandchildren most likely will even benefit from the low wages the illegal immigrants accept doing work that was previously done by the 26.7% of the black population living in poverty in Philadelphia, but is that a reason not to care?
So, to be crystal clear... no one is talking about "all blacks" or "stereotyping" blacks as only performing low wage jobs.
Trump is appealing to trying to bifurcate that black vote which historically has been overwhelmingly Democratic.
His messaging resonates with many blacks that are living in urban areas and who are competing with illegal immigrants for jobs and that includes over 25% of the black workers in Philadelphia (as an example).
Trump has also appealed to those African American blue-collar middle-class workers in the mid-West who are seeing their jobs threatened by EV production and outsourcing. Are they the only ones threatened by such things... of course not. But for the most part, white blue-collar workers have already gravitated towards Trump, but black blue-collar workers until recently remained loyal to the Democratic party... in fact Democrats frequently got over 90% of the black vote.
So, Trump is doing the opposite of what you seem to think. He is trying to granularize African Americans into different groups based on their economic situations and is appealing to that rather than saying, "if you don't vote for me, you ain't black". He is not targeting you. If you are a conservative, you already vote Republican, if you are a progressive liberal, you will vote Democrat. People with economic security can vote their ideology, people without it, need to consider their wallets.
In summary, for low wage African Americans, he is pointing to the negative impact of illegal immigration on them. He is not telling them something they don't already know, he is telling them he "gets it". To blue collar African American union workers, he is pointing to the adverse impact of EV production pushed by Biden on their jobs in Michigan, Ohio, and other Midwestern states along with impact of outsourcing US production. Again, he is not telling them something they don't know, he is telling them he is aware of their plight and plans to ease it.
Trump success has been that he is an opportunist and for all his talking, he listens to what people are complaining about and then decides if he can fit their concerns into his America first populist ideology. For low wage African Americans and middle-income blue collar African Americans, he can. In his first term, his First Step Act targeted African American families who family members received excessive sentences based on their skin color (again that does not apply to African Americans, but I think 5% of African American men suffered from Biden's crime bill from the early 90s).
When you move up the educational ladder, Trump did eliminate the need for HBOCs to come hat in hand for funding every year. That has a less direct impact on middle- and upper-income African Americans, but it a good thing generally speaking for African Americans.
Trump has promoted school choice in urban areas with failing school systems. An important issue to many African American families and not so much to others.
I could go on, but the bottom line, Trump is not treating African Americans as a monolithic group the way Biden referred to them, but instead is looking at which African Americans have needs he can address with his platform and which ones he is unlikely to reach. He is ignoring that second group.
https://cis.org/Oped/Time-Discuss-Impact-Immigration-InnerCity-Blacks
https://news.vanderbilt.edu/2007/11/01/illegal_immigration_hurts_african_americans/
https://cis.org/Testimony/Illegal-Immigration-Impact-Wages-and-Employment-Black-Workers
https://www.nber.org/digest/may07/effects-immigration-african-american-employment-and-incarceration