The unexciting answer is that they generally had the same economic views in the 1860s and 1870s as they had before they were Republicans. The radicals are a heterodox (and unstable) group who agree almost only on what to do about slavery and how to treat the South. That's fine in a single-issue party, which is what the GOP is until around 1866. Once slavery is gone and they're no longer operating as an ideological vanguard sort of movement, divisions between former Democrats (generally opposed to state intervention in the economy, including tariffs and supporting industry) and former Whigs (generally for) become more salient again. There's not a lot of movement between them, so what eventually shakes out is a GOP closer to old time Whiggery than old time Democracy just because there are so many more former Whigs in it.