At FL410 and ISA, 0.74M is roughly 217 KCAS with 0.77M being roughly 227 KIAS and 0.70M being 204 KCAS.

In the case of FLG3701, they started their climb at FL370 & 200 KCAS or roughly 0.64M and began a 0.1kt/second deceleration in the climb @ FL380 until level-off at FL410, at which time they were at 165 KCAS (0.575M) and still decelerating. At 150 KCAS (0.525M), the shaker fired.

A stunning display of ignorance regarding their aircraft's capabilities and high-altitude aerodynamics no doubt...but these guys would have been just fine if they'd have accelerated to & maintained profile climb mach speed.