An educated reader who knows the history may immediately understand the intervening logic.

That would indeed become cumbersome if every obvious intermediate proposition had to be spelled out.

But there is an important qualification

The issue is not simply whether the reader is educated.

The issue is how controversial or consequential the conclusion is.

An informed reader can understand the reasoning, but the historical consequence is more substantive, so citation and/or explanation become more appropriate.

And:

If that is a much stronger historical claim and requires considerably more evidence.

So I would distinguish:

Obvious logical consequence that needs little explanation

Reasonable historical inference → some explanation/citation useful

Controversial causal or motivational claim → substantial evidence required