TRC was flooded with hashpower, I think they 51%'ed it as well to orphan other miners blocks. The difficulty was jacked up through through the roof, then then left.
https://bitcointalk.org/index.php?topic=261986.0This is the downside of short interval difficulty adjustment. The two week one on bitcoin may be annoying but the short ones are open to far more abuse.
It wasn't just a flood of hash power, it was a bug in the difficulty adjustment someone was exploiting so they could mine blocks for their attack at 5K difficulty even if everyone else was on a far higher difficulty. Can't win that battle. Hash power coming and going isn't a problem for TRC because of the EMA difficulty adjustments, which were added earlier this year when hash power could mess things up.