Trump went out of his way in his Pence press conference to note the new huge manufacturing facilities being constructed in Mexico to access the US market with goods formerly manufactured in the US.
The multinationals building these plants have a huge capital investment in these plants and in Mexican politicans.
Jeb and the GOPe are their political agents in the United States to secure their financial interest.
Jeb in particular is a weird case. He has some strange psychological condition in which he is more enamored of and loyal to Latin America than to the United States. Everyone knows he married into a Mexican family and speaks Spanish at home. Not as many know he was a banker in Latin America for a number of years.
He arranged his life to capitalize politically upon the coming changes, and is livid that somebody's upsetting his plans so carefully laid long ago.