Bolvar was still himself when he just lost to Sylv, he had not given his mind over to the power. Arthas gave completely into the power. Bolver was the LK that the world needed to keep the scourge in check, Arthas, however, was the stronger one - by far.
You already knew there was no two hand frost. Blizzard has stated 3 expansions in a row there will never again be two handed frost. And all she did was destroy a helmet. Bolvar isn’t dead. There must always be a lich king.
Sylvanas: raised by previous Lich King as a banshee (basically a pet). Attempts to 1v1 the LK (Halls of Reflection?), gets stomped and forced to retreat.
Same Sylvanas: one shots the new LK, who is infused with red-dragon flame, as he was accompanied by the garrison force in Icecrown citadel, without taking damage…
I’m pretty sure some beta paladin made this cinematic as a smear tactic against our kind.
Didn’t the how for this get covered? Her shenanigans with the Maw have been feeding her with Anima from the dead. That’s a whole NE genocide coursing through her veins now.
It’s simple to understand why only a small amount of the Undead forces could be commanded to attack her.
Firstly we all know that it takes time for the Lich King to build up in power and technically Bolvar is a new Lich King so still learning and understanding the power he commands etc.
Secondly they are Scourge which are technically risen from the Shadowlands to life and if you consider that Bolvar holds no actual power within the Shadowlands itself while Sylvanus hold from what we can tell considerable power and authority she could quite easily break his hold on the Scourge that aren’t in the Lich Kings Proximity.
So the Lich King could only summon a small force based on his current new rebirth and wouldn’t be able to summon additional forces potentially because he was being blocked by Sylvanus.
Consider that the Jailor of the Maw which appears to be a Void Entity of some sort serves Sylvanus’s will and that she has much greater power base in the maw in shadowlands and you have your answer.
If we want levels the Lich King would be like a Level 1 players trying to kill a Level 120 player being Sylvanus in terms of her current power.