I just took a quick look at free practice 3 (figuring it would be easier
to find an in-car shot showing the data overlay), and found one of Lewis
Hamilton (start from about 14:12 in the video on F1TV), and you can
clearly see that at the same point in the corner where Leclerc's rear
tire is spinning up, Hamilton isn't near full throttle.
Hamilton only goes to full throttle just as he touches the second apex
of La Bosse.
At the same point in the corner where Leclerc's problems began, he's
using what we call "maintenance" throttle, and sure, he's even varying
the throttle to point the car a little...
...but that points up this:
'[Binotto said:] “There was a damper which was slightly sticky. Not more
than that. And we already put in place some actions to avoid it for the
future.”'
Well imagine if you're playing the throttle up and down to steer the car
in the mid-corner phase...
...and the damper was slightly sticky AGAIN.
Leclerc could have added throttle to get the attitude of the car where
he wanted it... ...and if the damper was sticky, he might not have been
able to reduce throttle quickly enough.
I have no way of know for sure, but it seems very much like Leclerc is
in a phase of the corner where there is no chance he'd be adding enough
throttle to light up the rear tires. This is an F1 driver with many,
many laps of that track, and by this point, he knows where you can add
throttle, and if you're pushing a little you might apply it a few tenths
of a second early...
...but not more than 2 SECONDS early.