The $1.7 B is a temporary measure to fund researcher salaries and research costs.
It's $134 million over three years to bring doctoral and post doctoral students over from the US, which isn't temporary, and doesn't mean it will end in three years, it just means that's how far out they've budgeted funding for at the moment. They're not going to be doing a detailed budget for these years out from now so it's entirely likely that program will just get extended if it's successful.
Then it's $1B over 13 years in new grants, which may not be as much as the US, but is not nothing and is not temporary.
And lol if you think researchers are going to want to go back to the US or will be welcome back to the US in the short to mid term. They elected Trump on two non-consecutive occassions. If those researchers don't come here they're going to the EU, UK, Korea, Japan, India, etc.