Tech has ALWAYS backed more H1B visas. This is nothing new. It's been the case for the last few decades from my experience. So it's no surprise Musk would push Trump to do a carve out for H1B's.
H1B's may be expensive to the company up front but it also locks in an employee at what is likely a sub-market wage and the employee is kind of stuck there. In order to move the employee would have to get ANOTHER company to be willing to front the cost of the visa etc.
And, yeah, there is a bit of lack of US talent. Not sure how "real" that is...there's still a fuckton of amazing engineers walking out of uni's here in the states every semester. I think the KEY is more that an H1B visa will be more "compliant" and less likely to bolt for higher pay, at least for a while.