Technically, I’d say “increasingly inevitable” is a meaningless phrase. “Inevitable” is an absolute - an outcome either is, or is not, inevitable. Like they say, “you can’t be a little bit pregnant”, outcomes cannot be a little bit inevitable, or somewhat inevitable, or mostly inevitable, so the degree of inevitability cannot be increasing.

However, I think most native English speakers would not think twice about it, and would read it as something like: “a Trump dictatorship is approaching inevitability.” That’s how I read it, at least.