So, in a very recent interview about transformations, Akira Toriyama explained how the Super Saiyan transformations worked. He says the following:

(Note: The boxes and Tori-Bot are all of Toriyama's responses)

Essentially, to go Super Saiyan, a Saiyan must have a certain amount of S-Cells that can only be activated through emotion. Once activated, the cells do not deactivate. The BEST way (not the only way) to increase S-Cells is through having a gentle spirit. So, Goku easily obtained Super Saiyan is because he had a high number of S-Cells combined with a high power level. Add that with the rage catalyst and you get Super Saiyan. It also explains why Goten and Trunks can do it so easily as well. It's because the cells are inherited from their fathers. 

Now, this isn't stated in the interview, but it makes sense. Because the Universe 6 Saiyans are more evolved than the Universe 7 Saiyans, they have more S-Cells. On top of that, they live rather gentle lives in comparison to their Universe 7 counterparts. Add the fact that the emotive point of the body is the upper back (explained in the previous post), and it makes total sense as to why Caulifla and Kale could go Super Saiyan so easily. 

However, I do have a theory on Berserk and Rose. I believe that Kale's S-Cells developed differently causing her to have a different transformation while for Rose, I believe that Zamasu's Kai cells infused with Goku's S-Cells to create  Rose.

Also in this interview, we get the name of the first Super Saiyan/Super Saiyan God (Yes, he is both.)

Anyways, that's essentially the real explanation to how Super Saiyan works but like with everything, all the "OG" fans won't accept this because they believed that the original explanation made sense. I want you to think about it really hard. The original explanation was that Goku turned Super Saiyan because he was pure-hearted and through rage. That's literally two-thirds of the equation. Like with how ki works, it had the spiritual energy (pure-heart), the emotive energy (rage), and was only missing the physical energy which would the energy from the S-Cells. 

Yes, it does seem like Midichlorians from Star Wars, but it makes more sense to me than Midichlorians. Also, to anyone who doesn't like the S-Cells idea, I don't know what to tell you. It just makes sense to me.

Anyways, have a good day!!

Some tags on people that I want hear opinions from!

Batty_And_Bubbly
DaddyGoku
Gokuisthegreatest
HayleyDBZ
DBZL0V3R
AllieQueenChan