There are a few things going on in the play. First, the TE went in motion from the backfield to the line of scrimmage pretty quickly after the initial shift of players. There needed to be a second stop before he went into motion, otherwise it is considered part of the shift. Second, right as the TE was finishing moving forward, the wide receiver went in motion. Third, the wide receiver never comes to a complete stop and may have been moving slightly forward at the snap (very slightly).
If the line wasn't set for a full second before the TE went into motion, the motion is considered part of the shift and then there needs to be a full second before the WR goes into motion otherwise that is also part of the shift and again the WR would need to be set a full second before the ball is snaped. Illegal shift.
Even if the line was set for a full second (it wasn't), the WR and the TE are very close to moving at the same time, which would constitute a second shift and again require the wide receiver to stop for a full second before the ball is snapped. Illegal shift.
And, if the WR were moving forward at the snap, everything else could be fine and it would still be an illegal shift.
The call was pretty ticky tacky because everything was right on the line of potentially being legal.
Here is a rule summary with video from the NFL addressing the same situation: https://operations.nfl.com/the-rules/nfl-video-rulebook/illegal-shift/