When Bitcoin was 20k, everyone had estimated 45-50k$ price for this year. Therefore it is difficult to predict a long-term price from regular way in crypto trade. Because the price doesn't have a regular movement and even a small move can influence the price movement.
In this article they just calculated the average prices of the prices and estimated. If it is so easy why do so many people lose money?
You cant say everyone. When Bitcoin was 20k in December last year, then many believed it will go further up. You never know that. Some predicted that is ATH. Some, and were many such believed that ATH should be way earlier. I remember Charlie Lee was calling ATH at $5k.
Once ATH was reached and price started declining anyone that was here in 2013 and is sane should know that we will have a year or two of bear market. And price will go down by factor 3 to 4. Yes there are lots insane people here also.