This is estimated to be a $12B project. $6.5B raised so far: $3B grant and $3.5B in tax-exempt, "private activity" bonds. Does anyone actually think the rest will come from investors? Of course not, the government will see a half-finished project that it supported and provide the funding to finish the job, including the inevitable overruns.
A private company receiving 6.5B (and likely, eventually $12+) of government money... no pressure or expectations to make any profit. Great deal if you can get it!