Why does "porque" seem to negate the subjunctive with verbs of feeling?

Question

I was glad that my father came to see me=Me alegré de que mi padre viniera a verme but

I was glad because my father came to see me=Me alegré porque mi padre vino a verme

and

It saddens me that my father came to see me=Me entristece que mi padre viniera a verme

but

It saddens me because my father came to see me=Me entristece porque mi padre vino a verme

I have seen this with other expressions of feeling and when I put it into various translators I always get the same thing. I realize that changing from "that" to "because" slightly changes the meaning but why does it go from subjunctive to indicative in going from "que" to "porque?"

Answer

I'd like to hear the answer on this as well.

My guess is that we only use the subjunctive in subordinate clauses.

Me alegra [subordinate clause beginning with "que"].

But when we use "because" we don't have a subordinate clause.

Me alegra porque [independent clause].

Hope this is right! I've been enjoying learning about clauses.