the most important question investors need to anwers

The market is expensive. Yes. 

But, is the market going to crash 50% like some thought?

To answer this question, one need to answer another question.

Where we are in economic cycle.

If you think were are in the late  cycle, maybe a crash is likely?

However, I would argue that we are in the mid cycle. With moderate inflation, and pro-growth economic policy, we may see a soft landing. 

In this senaro, or if Trump can engineer a soft landing,  it is hard to see the market crash ( dooms day type of crash). 

Of course, because the market is expensive, it could be volitale. 

10% type of correction is not unconceivible.

How  I am investing now?  I reducted my risk (removed beta leverage) and still have long exposure to US market. Will keep investing like we are in mid cycle,  but keep eye on risk.