In other words, Bernie thinks for himself and not as part of a herd.

He isn't a part of Group Think. He has a 40 year long history of working with the Democrats, for the people.
People who insist on using party labels for a person, such as Democrat/Republican/Independent, instead of using where a person is in the political spectrum, are purposely muddying the waters to confuse the issues.

Democrats and Republicans have switched places in the political spectrum from which they started. The Republicans used to be the liberals and Democrats used to be the conservatives. So we need to start using Liberal/Conservative, instead of party affiliations when describing people running for office.

There are many former Republicans in the Democratic party now, because the Dem leadership has moved so far to the Right to align with many Republican's world view.

What has not changed is whether a person is conservative or liberal or somewhere in between. Burnie Sanders is a liberal working for the people, regardless of party affiliation. As a result, the people are financing his campaign.
Hillary is financed by the same 1% big money backing as the Republicans canadates are. And that is why Bernie is being supported more and more by those who know about him, over Hillary's high profile name recondition, backed by the 1% to maintain the status quo.