Channeling Seth at times led to Seth channeling a second entity above him

[Aion]

I wouldn't say that Law of One has become more popular than the Seth channeling, personally. In my experience more people I've met have been familiar with or heard of Seth and very few are aware of the Ra Material. I actually haven't met anyone else who has read Messages From Michael.

I think Alice Bailey and Theosophy has dominated much of the field of channeling after Edgar Cayce. A lot of the "Ascended Master" stuff comes from those.

However, I would say the most 'popular' is actually Kryon, who spoke at the UN through the 90's. Obviously a later time period. Funny enough, perhaps not so well-known nowadays.
https://kryon.com/k_un.html

Interestingly, he started channeling Kryon in 1989, a being whom claimed to be part of the same 'family' as Michael.
I was also born in 1989, my middle name is Michael, and well, I'll just leave the curiosity at that.

Oh I would also mention the St. Germain channelings by Guy Ballard have been very influential, being one of the core 'Ascended Master' ones. Although weirdly there's a split between New Age and Theosophy with each kind of having their own idea of the "Ascended Masters" and I think this convolution has lead to immense confusion between the two.