HFT financial engineers can not necessarily learn software engineering in their operating time-frames. There is no "High Frequency Learning"; by the time they learn to configure a development environment they could have lost the edge.
It's a lot easier for a good programmer to learn how to trade than for a good trader to learn how to be a programmer. Though most programmers make terrible traders and most traders make terrible programmers. A lot of depends on the company you are at, the more foresighted ones, were grooming guys for this role 5-10 years ago. And more importantly establishing a tradition of `trade developers.` Typically though the traders that become good enough programmers took an engineering discipline in college. Also, some of them are just so smart / driven that coding something good enough to make money is something they trudge through, but their code usually the ugliest thing you'd ever see this side of php.