Okay. Here's the thing with Mamamoo (from a former fan).
I started following them when they first debuted. Anyone remember the old youtuber MrJKpop? The one who used the fact he had underage fans watching his reactions to end up approaching an underage girl for sex and sending her lewd photos? Yeah, well before that disgusting news came out, I and many others loved his channel (he was one of the first reactors who actually knew something about music so his analysis was more interesting compared to others at the time). He interviewed Mamamoo when they first debuted, and that's how I starting getting into them.
Though I'm sure they probably have some shady symbols in their earlier music, after all it is kpop, I don't think they'd sold out at the beginning. If there were symbols, I think on the group's part it was probably unintentional (not to say that the company wasn't aware, I just don't think the group members were at that point in the very beginning).
The mark I'd set for when they sold out would be Decalcomanie. I think Um Oh Ah Yeh was what got certain peoples attention, I think that comeback was their company making an attempt to reach out to those in the "higher positions of power," a plea for the group to be let into that elite level. Decalcomanie was what followed, and it signified that they'd been let in. "You're the Best" happened in-between, and when it came out it became their most popular song to date. It really solidified the Korean public's attention. Now that the company had made it known that they wanted to sell out to the elites, and now that the group had the adoration of the public, it was time for them to fully sell out. That's when Decalcomanie came out. That's when the sound of the group started changing.
I feel like "Yes I Am" was their goodbye song to the old Mamamoo, to the old fans, and an ushering into their new sellout sound. And I don't just mean that in a "they make mainstream basic pop now," y'all know what I really mean. I had other friends who used to be into Mamamoo like me, they're also religious, and after "Yes I Am" came out none of us have been interested in any new Mamamoo song. Even my other religious friends who don't follow these kind of forums talked about how uneasy the Egotistic MV made them feel and how "Mamamoo has definitely sold out to somebody."
Egotistic was what solidified their selling-out on a more international level. I don't know what the group or their company had to do to get them to that level of fame, especially in the way they did (speaking of the types of MV's they have now). With their voices, I think it's possible they could have eventually reached that point on their own. But not this level of international fame this quickly.
Edit: should add that Mamamoo came from a similar situation as BTS. Both came from small companies where they were basically the main artist supporting the entire company, both do have some genuine talent, both sold out to the elites (arguably to different degrees but only time will tell for that), and now both have a new group debuting that benefits off of their fame to get exposure.
Should also note that the name of Mamamoo's company is "Rainbow bridge world" (RBW) Entertainment. Reminds me of Wizard of Oz programming, the whole idea that one must go "over the rainbow" in order to find happiness where all your dreams and desires come true. I definitely see a connection between the company name and the many LGBT references in their videos.