THQ bet big on the Wii-U with a large investment in uDraw, a drawing game that included a drawing tablet and stylus. They invested a lot into that game and had a lot of them produced expecting high demand. All that hardware meant the up front investment was incredibly high. When the Wii-U failed to take off, and sales of their game was way under projections as a result, they were in trouble.
They were already in a bit of a rough state prior to that, but nothing they couldn't have recovered from. uDraw went on sale at the end of 2011, in 2012 they defaulted on a loan of 50 million USD and were desperately trying to avoid bankruptcy.
That's when they went to Humble Bundle to try to raise some money by putting their games into the Humble THQ Bundle. That raised 5 million USD which was not nearly enough to pay off their debts and subsequently filed chapter 11 bankruptcy just a few days after the sale ended.
Regards,
SB