>>509018866
1. There seems to be dozens of different groups of aliens coming here, they all seem to have different agendas so they may be preventing one another from doing anything drastic. Basically, think of the cold war with more than two sides.

2. Crashes may be deliberate to provide specific technologies at specific times.

3. If they're hyper-intelligent then it's likely they can think of ways to achieve a specific goal that is infinitely more subtle than we can.