Why? It's a very well explored and prominent example of a population 'collapse' leading to long term rejuvenation (and innovation).
I'm not pretending that some of the short term to medium term consequences of a population 'collapse' (I keep putting it in quotes because it's your word and I think it's too emotive a word) won't be dire. But at some point a population has to go through a period of decline. We see this all the time in the natural world. People who don't want to have any periods of decline and go all Pollyannish with emotive talk of 'collapse' and worse for any period of population decline seem to be stuck in a fantasy world, in my opinion. Not the real world, where, to slightly belabour a point, animal populations go through cycles of growth and decline, repeatedly.
And raw population numbers are the least of the problems here. The comparison to the Black Death is rather silly.