YC is definitely pivoting into Defense. Besides 9mothers, there’s a list of 22 defense startups accepted into YC just this year so far:

https://www.ycombinator.com/companies/industry/defense

And beyond this there are a number of defense-dependent companies like ProvenMetal (whose value proposition largely depends on a customer’s deep need to do onshore manufacturing)

It makes sense. From 2000-2015 it was pretty difficult for anyone to break into defense and really own a brand. Breakout companies like EOTech were really rare. Generally founders would be at the mercy/grace of the major defense incumbents ('primes'), getting scraps from their tables.

That’s changed lately. For a wide variety of reasons (political, technical, and on active battlefields) there’s a lot more room for startups to really own their own slice of the industry and build some moats of their own.

they invest in defense stuff now, that's new!

but. paul graham doesn't like defense stuff. there were plenty of great defense seed investments (palantir), and he runs the best seed venture firm in the world, always has, so his opinion matters. but it was out of a righteous place, it wasn't because he thought it couldn't make money.

y combinator is a much bigger fund now with lots of people in charge. the "2000-2015" era you are talking about: valuations of everything were 1/10th of what they are now. it's hard to make any definitive comparisons about venture trends.