1. (Gardening) A bed of earth heated by fermenting manure or
other substances, and covered with glass, intended for
raising early plants, or for nourishing exotics.
2. A place which favors rapid growth or development; as, a
hotbed of sedition.
So the metaphorical use for "hotbed" is pretty old. Why did Forbes choose "hotbed" for a place that grows radical politics and "seedbed" for a place that grows businesses? (See previous post.) Possibly, it wanted to tap into the "fermenting manure" imagery or to suggest that radical politics only grow in an artificial, glassed-in environment. A Google search for "hotbed politics" produces 37,000 returns. "Seedbed politics" only returns 5,160. "Seedbed business" produces 15,000 returns. Ah, but "hotbed business" brings in 79,700, so now I need a new theory! The new theory is, people just like the word "hotbed." It's more exciting.
So, Forbes, the hotbed didn't become a seedbed. Madison was and is a hotbed. But something different is growing in the hotbed right now. Same hotbed, different flora.