Know how the market worksAs a rule, an acquirer's stock after such a transanction goes down because the its stock either it's dilluted if the acquisition is by means of conpamy's stock or through debt and cash as is the case with CRH. That is because its overall value gets lower until the company begins to produce revenues and earnings. If earning go up in the future, the stock will recover in time, but at the time of the transaction the stock takes a dip. And the short sellers know that. But in the next few days or weeks the stock will likely recover and even go higher.