They didn't drop much on their main markets (USA and UK), in fact they tracked ahead on those for about 3 years, so how would you explain almost zero impact on their main markets with they dropping dead everywhere else? Did only people outside of USA and UK watch the presentation?
They took several years to be able to put the price on market acceptance while never being cheaper than X360. X1 solved most of the issues even before release (always online, DRM, TV, etc), had more exclusives at launch and before even 1 year in the market always sold cheaper than PS4.
There are way more dedicated xbox fans in the USA than anywhere else. It's the only reason why is sold well in the USA initial. Xbox isn't nearly as popular in the rest of the world to begin with compared to Sony, so once Xbox lost most of them, it was over, and they went to the PS4 instead.
It doesn't matter. Once that word of mouth spread about what the X1 was doing, people jumped ship. I knew people that didn't even know X1 fixed most of the issues, 2 years later. The damage had already been done.