The reason is because... "X".
The reason is that... "X".
The phrase "the reason is" implies a causal relationship between two events or states. For example the reason that the wagon is red is that I painted it with red paint. The wagon being red is caused by my painting it. I could also say the wagon is red because I painted it. Cause: I painted; effect: it is red.
So If I say, “the reason is because,” what I really am saying is that the cause of there being a reason is that I painted it. This is akin to saying, “I painted the wagon and that is why it is red because I painted it.”
So, indeed No. 1 is a redundancy, a grammatical error, and a logical violation. Much like saying “ATM machine” – (a machine that makes ATMs I suppose), or that something “is comprised of” its constituent parts. But I suppose those are separate topics.