I keep going back and forth on if Ian was always always stupid.
I think he was just at the right place at the right time. Personally, I think he was always a spineless little shit, but there's no denying he had more charisma and more energy back then, and above all, he didn't take himself too seriously. His current "everything is political" stance just reeks of snark and Reddit-tier brainrot.
I put him in the same camp as DSP, Wings and OnlyUseMeBlade - guys that, by sheer coincidence, were at the forefront of their respective areas. These three became successful (though not nearly as much as Ian) not because they were super talented MLG players, they were simply at the right place at the right time - the gaming commentary and let's plays were just beginning to become a thing, and, at a time when there wasn't much choice, they were the best at it. Say what you want about Blade, but he was one of the pioneers of the whole "challenge gameplay" thing on Youtube. Besides, in the 2010's, the audience had much lower standards for content; at this point, having a functioning mic and a potato facecam was peak content. These three all failed and became lolcows for different reasons than Ian, but they sort of share the same career slump.
Ian was pretty much one of the first people to popularize drama content and call-outs/takedowns, that's the only reason why he got so big back in the day. The commentary community was very much in it's infancy - the only real competition he had was Leafy, Keemstar and maybe GradeAUnderA. Ian was just smart enough to make videos taking down the easy targets that nobody liked, and let's not forget that, at that time, simply saying "nigger faggot" made whatever video top-quality because we were all edgy teens at that point. I always found the skits to be cringy, but skit-humor was mega popular in Youtube at the time.
Ian was never good or funny (even though he had a lot more charisma back then), he was simply an awkward fag with a camera that, by luck, happened to make pioneering videos that people really enjoyed. Youtube as a platform wasn't nearly as popular back then, most of the audience were late teens and people in their early twenties, and it just so happens that that type of content was really popular with that kind of demographic. To my 19-year old brain, going around saying "nigger faggot" was super fucking based and red-pilled. Nowadays, it's just cringe.
Ian is stuck in a loop of thinking "I've matured", but he completetly ignored that so did his audience in order to shield himself from criticism. The kids in his comment section now have jobs, families and money in their bank accounts - but because Ian is frozen in 2016, he thinks everyone else is frozen in 2016. That's why he thinks that breadtube is going to be the next big thing.
Also, let's not forget that Youtubers only have like 5 years tops of good content, then they start to decline. Even huge people like Phil DeFranco, Pewdiepie, Markiplier etc. are nowhere as big as they once were, despite still having a big reach and being regarded in a positive manner. Thing is, most creators start to see the slump coming, and just quietly quit and take their money and go do something else. Not Ian, though.
TL,DR: Ian was never a great content creator. He had some charisma and a small amount of talent, and a HUGE amount of luck of being at the right place at the right time. Also, saying nigger faggot in 2016 was pretty funny and based, no matter who you were.