Weird Market, weird analysts, weird "investors"

Do you all ever notice, when a company do well in a single quarter year, all analysts mark up the target price of the company, and when a company show a bad result in a single quarter year, they turn down their target price.

How can a business be valued just from a single quarter year result? Will you go and buy a business, and tell the current boss "hey boss, today your business seems terrible and no customer at all, I think your business worth nothing! I think I buy it from you at 50k! (actual worth 100k)".

What do you think the current boss will answer you? He must think you are crazy~

But this is actual how the market looks like, the market analysts and those so called "investor" are judged a business by just a single quarter year result or is it any theme play on this industry.