Mtgox was an exchange that launched in 2010 and was the biggest bitcoin exchange in existence until 2014. The exchange originally was not meant as a platform to buy and sell bitcoin; The platform was originally created to buy and sell “Magic: The Gathering” playing cards.
The website later on started selling and buying bitcoins and became very popular because it was one of the few places where this could be done. The company only operated until 2014 because it discovered it was missing 850.000 bitcoins, at the time worth about $450 million dollars.Once the company found out it was missing all the bitcoins, it halted withdrawals and declared bankruptcy.
Since Mtgox was insolvent, the process of giving back the bitcoin holders a share of the bitcoins they had deposited began; but while the process was trying to pay the creditors bitcoin back, the price of bitcoin increased significantly. The price of bitcoin increased so much that Mtgox had enough bitcoins to pay the dollar equivalent of what was owed at the time of the bankruptcy. This made Mtgox solvent again because it was able to pay it’s debts; this would allow it to potentially do more business in the future.
There are various theories about how the bitcoins from Mtgox disappeared; some believe they were hacked because of a vulnerability in the code at the time, others say it was mismanagement by Mtgox, while some people believe it might have actually been people inside Mtgox, if not the owners themselves, to take the bitcoins and pretend they were stolen.