Who’s idea was this?
Probably Vivek Ramaswamy. Trump just tends to agree with the last person he's been talking to -- provided said person has probably stroked his ego -- no matter what the issue at hand.
He was on a podcast with Silicon Valley VC types, who were immigrants themselves. And they want this for cheaper STEM labor.
And being Trump, he wants people (especially rich successful people) to like him, and he says what they want to hear.
If you listen to the recording, it’s Trump riffing on something that polls well with the undecided voters he needs to win.