It's true that a majority is from the US government through various funding schemes and grants. They're very transparent about their funding and ongoing efforts to diversify. But a little over half coming from US government sources isn't the same as their devs literally being on the gov't payroll; people often talk about Tor as if the developers themselves earn a government salary.
(Funnily, Signal also received major funding from US government sources but very few people seem to question that when lauding Signal.)
Even if you had your own SMT how can you be sure no one fiddled with your lab? If you can't trust your own stack 100% how can you trust ANYTHING else then?
So my answer to your sincere question: no reason to believe it is safe, no.