Unless they do, or are severely weakened. Consider the net worth of the 1% over the last few decades. Even corrected for inflation, its growth is staggering. The wealth gap is widening, and that wealth came from somewhere.
So yes, when there is an economic boom, investment happens. However, the growth of that top %1 tells me that they've been taking more and more off the top. Sure, some near the bottom may win with the decreased labor costs and whatnot, but my point is less and less do every cycle.
Full disclosure: I'm not an economist. Hell, I probably have a highschool-level of econ knowledge at best, so this should probably be taken as a "common-sense" take on it, which I already know often fails spectacularly when economics is at play. So I'm more than open to be corrected here.