Risk is turn-based while HoI is real-time. HoI then adds a thousand layers of complexity and there are lots of other differences of course, but I think real-time gameplay changes the pace and feel of the game fundamentally.
Silly little animations and boom booms are unneeded fluff in these sorts of games. I can't really remember the music in HoI4 but I do remember Darkest Hour having a wonderful soundtrack. It tends to have lots of strings and percussion and brass and is very sweeping and marching and pensive and fits very well with the tone of the game. I think it's very cool!
(I also thoroughly enjoy a nice bit of toast with just some butter on it. I had some toast for dinner yesterday!)