It's a bit more nuanced than that. Markets react to all available information, and halvings are publicly known beforehand. Litecoin rising from $22 to $146 in the first two quarters of the year was likely the market "pricing in" the halving. Litecoin outperformed BTC and the rest of the altcoin market during that period and I think halving hype was likely the cause.
That's what BTC did in 2016 too. It rallied hard into the halving (doubled in price) but crashed a month before it. And then it kept crashing afterwards.
Buy the rumor, sell the news.