The US Government wanted companies to build fabs in the US so it offered them money to do it. Intel, which was one of those companies, but not the only one, took them up on the offer and was paid to begin construction on a fab in the US.

Normally when we pay businesses to do things we don't demand equity stakes in the businesses afterwards.

Notably, the biggest shareholders in Intel appear to be retirement funds of Americans - so Trump has just pilfered some money from the retirement accounts of Americans.