This is pretty typical investor behaviour "buy the rumor, sell...

This is pretty typical investor behaviour "buy the rumor, sell the fact". So large investors and traders take advantage of good news to sell into a price spike where there is lots of liquidity and plenty of transient demand. They know that in doing so and cashing up, they limit the price rise and as the news subsides in the coming weeks they can buy back in at a lower point after taking a profit.

Some people (incorrectly) label this as a "pump and dump" without understanding where the phrase comes from.