The front-month implied-volatility rises into the date because one session now contains most of the expected movement. After the release the uncertainty is resolved and volatility collapses — iv-crush — regardless of which way the stock went.
This makes direction insufficient. A long call can be right about the move and still lose, because the volatility it paid for evaporated. Structures that are short volatility on both legs, or that use the expected-move to set strikes, are the usual way to trade the event rather than the news.
Example: XYZ at $50 the day before earnings, 7-day implied volatility 68%, straddle $4.10 implying a $3.50 move. XYZ opens up $2.20 — a real move, less than implied. The $50 call goes from $2.10 to $2.35 while volatility falls to 29%. Right direction, almost no profit.
Related: iv-crush, expected-move, reverse-iron-condor, volatility-term-structure