Erm, such as?
The actual report actually lists a bunch of factors that support their opinion, so maybe they're talking about a number of these going off the mark:
https://data.bloomberglp.com/professional/sites/10/Bloomberg-Indices-Outlook_Cryptos_June-2020.pdf
To name a few, and each of which has a writeup:
History Indicates Bitcoin Toward $20,000 in 2020
Maturing Bitcoin Gaining Upper Hand; Nasdaq, Crude Oil as Guides
Grayscale Trust Absorbing Bitcoin Supply
Bitcoin Futures May Be a Driver to Sustain Above $10,000
$8,000 Bitcoin Base - Transactions, Hash Rate
There are a lot more, but those are what primarily caught my eye. The report seems to be worth a read, at least.
It also has to be noted that the $20k prediction was brought about by following the 2016 pattern, which they did not say was a given. It mostly just states that there are a bunch of factors which mean Bitcoin is practically guaranteed to appreciate, not necessarily by a lot. This is just another case of a clickbait article oversimplifying stuff.