Because as you can see in the image @OP posted, Google considered that for the query 'Bitcoin", the person is looking for information about Bitcoin.com hence it displays a paragraph taken from Wikipedia.

It's not a wrong answer, it's because Google doesn't make the difference correctly between Bitcoin and bitcoin.com.
Adding to the fact that the Google Core update is currently taking place during about a month or more, some results may not be accurate or relevant during this period until it becomes stable.

There are thousands of queries with a similar problem and it happens with every Google updates