spoilers:end of spoilers
It looks like he just stole their tech, to be fair - namely, Black Widow, Giant-Man, Iron Man, Thor, and Captain America. Natasha was a long dead traitor in 1610, and we know Tony had been replaced by Ironheart, so he couldn't have just defeated the Ultimates in battle, Widow wouldn't have been there. He also doesn't seem to have got anything from Spider-Man or Spider-Woman, who were both also on that Ultimates team we saw at the end of Spider-Men II.