Trump did start the lower cost of insulin train, but when he started it was only for “1,750 standalone Medicare Part D prescription drug plans and Medicare Advantage plans.” ^(1)

So yeah I guess he started it, but Biden actually did it with his Inflation Reduction Act, which Democratic lawmakers pushed through Congress in 2022. ^(2) (3)

(1) https://www.cms.gov/newsroom/press-releases/president-trump-announces-lower-out-pocket-insulin-costs-medicares-seniors

(2) https://amp.cnn.com/cnn/2024/01/01/politics/insulin-price-cap

(3) https://www.medicarerights.org/medicare-watch/2023/06/29/the-inflation-reduction-acts-part-b-insulin-price-takes-effect-july-1

Edit: sorry for the format on this one. I copied it from an earlier comment where I was being snarky