I don't think grunge had anything to do with their demise as they split up in 1987, way before grunge came along.
I really don't think they were ever considered a flash in the pan either, as the band had existed in some form or another since the mid 1970s, and they got their first taste of success in the UK in 82/83, and in fact it was the humourous videos that got them their foothold in their native country (the songs were certainly not humourous). Their biggest problem as that Stay hungry was such a huge hit that people felt Come out and play was a step backwards, and the band was already in turmoil by then. MTV refusing to play the Be chrool to your scuel, video. Poor concert ticket sales. And then AJ up and quit at the end of the tour.
Their biggest problem was that it took them so long to finally break through that by the time they did, the age old trope of band in fighting became their downfall. I remember several interviews when Dee was promoting Widowmaker, and he was incredibly harsh about the rest of TS. Claiming they had no talent and their idea of back vocals was just shouting etc.
I am a big fan of Dee, but I can imagine his big personality can be a lot to deal with in real life, and he certainly took over creative control of TS which probably pissed off the guys who were in the band before he ever joined.
Heard this today,it starts off well,the first few tracks are pretty good and Richard Black sounds well...but its downhill for me from about track 5 or 6 and I can't really recall the last couple as they passed me by due to my initial disappointment
I grew up in Maryland used to see shows at Network that later turned into Daytona then when I was old enough Hammerjacks in Baltimore, Frederick had big metal rock scene too I think it still does this is a great blog for metal in MD,dc and northern VA, https://dcheavymetal.com/