Vegapunk is famed as the greatest scientific genius the world has ever known, having tremendous knowledge and unmatched understanding in multiple, different fields of science, ranging from cell biology to military technology, as noted by Franky. His scientific expertise is said to be at least 500 years ahead of his contemporaries.
Vegapunk was once arrested by the World Government for his dangerous experiments in relation to research conducted into the Lineage Factor and cloning. Despite this run in with the bureaucracy, he was employed as their chief scientist in the Marines. So Vegapunk is being kept against his will, and is forced to make weapons. The Government isn’t watching his back, they’re watching his every move!
If someone like a Revolutionary approached him with a plot to overthrow the Government, he might listen to it. If it’s a good plot. And Dragon seems like a guy with some good plots.
But of course, Vegapunk can’t openly support them, and the less people know about his involvement, the better it is for him. So Ivankov doesn’t know he’s an ally. Hell, even Kuma might have been kept in the dark. At least, he seemed sure he would die if he went cyborg, which Vegapunk wouldn’t do, would he? Not, just because he’s secretly a Revolutionary ally.
Kuma was pretty mindless during the war, or just pretty amazing at the undercover thing. Ivankov is still alive, right? Or maybe Vegapunk is keeping his brain in a jar somewhere. At least, I think it’s pretty sure Kuma is gonna show his personality when the Government does not expect it, and it will be amazing. And Vegapunk is probably gonna need rescuing when his betrayal comes to light…
*Theory by Birdy