There are plenty of talented C++ programmers. They just don't want to be abused by trading firms or work in that culture. Even paying them more won't work, because no amount of money is worth that abuse.
I interviewed at a trading firm once, while I was working at Netflix (because Netflix encouraged us to interview for outside jobs at least once a year). The comp would have been double my Netflix salary.
But I would have had to work in their office in Manhattan, be in by 8:30am every day and not leave until after 5 at a miniumum. But that wasn't the part that scared me off. It was the fact that I would not be allowed to share my work internally. I would not even be allowed to brainstorm with people doing the same job in other areas of the business. I wouldn't be allowed to take my laptop home, so if I had a hard problem to solve, I'd have to stay in the office the whole time. So basically they expected us to never see our family nor collaborate with anyone.
Basically, they were so worried about secrecy of their trading algorithms and people sharing them with other companies, they didn't even let people share internally for fear that one person would learn too much about their business.
I decided to stick with my FAANG job because even the ridiculous money wasn't enough to make it worth the stress and isolation.