I am not sure the market for universal disc players is as small as you claim. Sony started making universal players a couple of years ago and that may have had more to do with Oppo bowing out, then the market being too small to mess with. Now Sony has a huge share of a small market. I believe there is a stubborn group that won't abandon discs for streaming unless forced to do so.
As far as Oppo entering the TV market, that is a puzzle to me since that market is very competitive and profit margins are thin. The high-end OLED market offers higher profit margins for LG but I don't think that is going to last much longer.
I don't know how you can view the disc market in any other term but shrinking...or declining...or on the verge of extinction...companies that used to make disc players stopped production...brick and mortar stores like Best Buy don't even sell CDs anymore....and universal discs players are a tiny niche market within the disc category...you even predicted the demise of the Big 2(MoFi and Acoustic Sounds) boutique shops 8 years ago
IMO it's irrelevant if Sony has a "huge share of a small market"....which is your contention... the market is shrinking..the reality is that Oppo saw diminishing returns on their investment and wisely decided to leave...