This is understandable, and is a fairly common dynamic. It's a 2 level principle/agent problem.

The goal of investors is to maximize their long term investment. They do this by using the limited tools available, such as paying management bonuses based on profitability, so managers don't simply exploit their position to be lazy, or worse, make small amounts of money at the expense of the company.

The personal goal of management isn't to maximize long term value, it is to maximize short term profits, as measured by stock prices. Long term investments are costly, and because it's impossible over the 2 year time frame to tell the difference between prudent long term investment and simply increased expenses, stock prices drop when expenses go up for any reason.