"But why would they do that now? Why not at a higher sp? Why sell so much to drive the price down? ( unless to cause panic and provide a buying opportunity in which case they would be buying back)"

Turr, not to cause panic, but due to it. And others figuring they could get back in lower after the offering. Not only are there lots and lots of shares represented here, some folk have POET as their only or certainly their disproportionately largest investment, and there were plenty of "scary" posts on Monday. I doubt any of the sellers sold with the intention of driving the stock down. But take a look at some of the most highly recommended posts from Monday, and you'll see what I mean.