Pulling the rug out from under someone is a term that's been around for decades.
In in songs and all kinds of other references.

In this case it's a pretty accurate statement to make.
Farmers are expecting to farm high yields for at least a year because the term APR itself is annual by definition. If yields decline massively all at once the "support" is being removed "suddenly". So fits the definition pretty well but is triggering in crypto because of how inherently risky crypto is to begin with.