Why are insiders selling? No one knows

It's important to note that while insiders must document when they buy and sell stock, they don't need to say why.

That means it's not clear whether insiders are dumping stock because they fear a market bubble or simply because they need to raise cash to buy a new home.

"Maybe they are literally just figuring out their own personal balance sheets. These are real people making real economic decisions," said Nicholas Colas, co-founder of DataTrek Research. 

Colas added that corporate executives may also be choosing to cash in chips because they fear for their own jobs as companies mull cost-cutting during the pandemic. 

"These aren't Robinhood traders," said Colas. "They are executives trying to figure out the right amount of cash in the bank in case they get laid off."