Unless you were sat behind the wheel at that time you, I, nor anybody else has enough information to make that call,
That's not true else no-one would ever be prosecuted for any driving offence.
we all do not know what field of vision the driver had. If he/she had clear vision down the cycleway in both directions then it was safe to proceed, [...]
If the give-way marking on the road is the regulation 3.75m long and the video timekeeping (at quarter speed) is accurate, then the van driver seems to take 0.4s to travel 3.75m, so is doing about 21mph on arrival at the give-way line. I'm sure someone with the original video could estimate it more precisely. While probably not lethal if there was a collision, I think that's still too fast to enter a crossing in a big van with thick A pillars that might obscure an cyclist approaching down the slope from the left slightly behind square.
Of course, the measurements and the visibility out of the cab would need checking if anyone was going to actually prove this to any standard, but I think it looks likely that they were going too fast. In one way, I'm surprised anyone approves of that intimidating speed of entry into a crossing against priority, but in another way I'm not because such bullying of more vulnerable road users is really really widespread in the UK.
I'm leaving aside the OP's non-priority as we basically agree there.