They're dominating largely because they've got the best team tbh. In their Tour squad alone, Castrovejo is a former world TT podium finisher and has a best Tour finish of 24th, Kwiatkowski is a former world champion, monument winner with a best Tour placing of 11th, Moscon is one of the best time trial and classics riders in the world with a best GT finish of 27th, Poels is a monument winner who was 6th in the Vuelta last year, Luke Rowe is a strong classics riders with top 10s in PR and Flanders, Bernal is one of the hottest talents in world cycling and a winner of the 'junior Tour', as well as this years Tour of California, and then you've got Froome and Thomas.
Add to that the likes of Henao, Ellisonde, de la Cruz, Intxausti and Diego Rosa who have all been either top 10 or top 20 in a GT. It's a depth of talent that few can match. Heck even Deignan and Kiry have top 20 placings on their palmares, whilst Geogan Hart is another hugely talented youngster.