Another quote for you viz "if ifs and buts were crackers and nuts every day would be Christmas". You don't seem to have any problem with making broad and confident assumptions/statements yourself while taking strong issue with minor points in posts made by others.Marquez is the best rider on the grid today, no two ways about that. In fact, had he ridden sensibly in 2015, he might have contested the title against Lorenzo.
My point, however, was that the Yamaha's results did not, in fact, deteriorate over the latter half of the season. At least for Rossi.
That's also a gamble in many ways. Superb as he is when the setup, tyres and conditions are good, Lorenzo might end up at the other extreme when the situation calls on him to ride around the problem (ref: FP3 Phillip Island 2016; 21st place behind Rabat).
There's no point finishing 15 seconds ahead of Marquez in one race, only to finish 5 places behind in the next one.
Still, Yamaha did put the 'best' contract he'd ever been offered on the table, he felt it was time for a change of scenery and assumed (not unreasonably) that he could contend for the championship on a steadily improving Ducati, a bike that had registered 8 podiums the year before, and almost registered a 2-3 finish at Qatar, all under riders who were good but well short of alien material.
Wasn't much Yamaha could do about that. Though given Vinales' long term prospects, it seems to have worked out quite well for them.
Rossi may not have cared in 2007 but I'd say Lorenzo definitely cared in 2016.
More importantly, if Marquez has a 2014-like season, neither Rossi, nor Lorenzo would have a chance. But Marquez isn't a sure thing - he was too close to disaster several times in the season and his pts cushion at the end wasn't really large enough to accomodate more than one major mishap.
And if something like that happened in 2017, a rider like Rossi who could be relied upon to be not just consistent but fast in all conditions & on all tyre types would be a stronger bet to capitalise on the situation. On Bridgestones, he finished just 5 pts behind Lorenzo. On Michelins, if not for the Mugello incident, he'd have finished 46 pts ahead.
It is what it is, the points tallies were what they were, I have no problem giving Rossi credit for his performances in recent seasons, but the facts are that he couldn't close the deal against Lorenzo in 2015 and that both his seconds to MM were distant, while Lorenzo pushed him quite closely in 2013, admittedly in MM's rookie season and with the PI debacle aiding Lorenzo to still be in the fight at the start of the last race. If I was to play your game in regard to Lorenzo being about to be passed by Dovi or Vinales or concerning Rossi putatively having a greater points margins over Lorenzo, then Lorenzo really should have 4 premier class titles since MM's margin was gained by what was imo and that of others an illegal move on the last corner at Jerez.
i have no idea how strong Lorenzo's motivation was to finish ahead of Rossi as opposed to winning the title last season, but for all we know he might have decided he didn't have Yamaha's full backing, that there was a tyre conspiracy against him, or even that the tyres were just substandard and he couldn't win on them, and have decided not to risk too much looking forward to this season with a new team on a different bike. I actually don't think there is much chance of him getting a tyre which really suits him at Ducati or was if he stayed at Yamaha, but he may have felt that Ducati would at least be all out for him, similar to Rossi in 2010.