Jamieson, Fausset and Brown on Daniel 8:24

24. not by his own power--which in the beginning was "little" (Da 8:9; 7:8); but by gaining over others through craft, the once little horn became "mighty" (compare Da 8:25; 11:23). To be fully realized by Antichrist. He shall act by the power of Satan, who shall then be permitted to work through him in unrestricted license, such as he has not now (Re 13:2); hence the ten kingdoms shall give the beast their power (2Th 2:9-12; Re 17:13).

prosper and practise--prosper in all that he attempts (Da 8:12).

holy people--His persecutions are especially directed against the Jews.