Republicans are not a monolithic entity.
There are people like Mitch McConnell, Mitt Romney and Megan McCain who are all right wing Dbags but see Trump for what he is. Aside from the tech bros like Elon Musk there are those in the business community that do not support Trump because they don’t have a seat at the table.
They failed just as much as Biden and the Democrats did to stop this.
The 14th amendment is very clear on this, and has been upheld by the Supreme Court on many occasions.
Unless you are the child of a a diplomat or an invading soldier you are awarded citizenship if you are born under the jurisdiction of a state I.E. US soil. Illegal immigrants are still under US jurisdiction and their children are awarded citizenship as a result.