Then explain how Van Aert, who's been doing significantly less CX for the past 4 years than Mathieu and has significantly less technical baggage, is now making significantly less errors. A guy like Hermans does not do more CX than Mathieu either and has become a road cyclist. Yet it is Mathieu, the technical wunderkind, that is getting stuck, doing headrolls, making technical errors in every race.
It could be pain which is making him uncomfortable on the bike (though the backpain has only flared up the past few races, while he has been bungling races over two weeks ago), it could be that he's physically on the limit and pushed so hard that he starts screwing up. But him, the personification of whatever constitutes the concept of cyclocross, losing skills because he doesn't train enough, while riders with less skills who do even less training, do not suffer of the same, can't be taken seriously.