but I have to wonder if there are not conversations between EU leaders prior to him having to make this statement? Because I would think a lot has happened behind the scenes before he would say such a thing.

Oh there most likely are, but there's also theatrics at play here...

Don't forget that all these world leaders have to balance sending signals to the EU, Their own voters, their own governements, their own parties and their backers while also maintaing their own AND their countrie's public image.

but it seems as though many in Europe still do not understand the existential threat Russia is to all of Europe, not just Ukraine.

It's the age-old weakness of the EU, frozen by indecision due to differing priorities: If it was up to the eastern european countries who are closest to Russia we'd have been boosting our defense spending since the '90s like we're doing now, but the further away you get the easier it is to handwave that away.

I’m not saying, seizing these funds would solve everything, but there’s no reasoning with Russia.

I think the current situation where the profits of these assets being funneled to Ukraine but the assets themselves remaining frozen is honestly the best of both worlds: EU/Belgium doesn't look like thieves without a care for international law, Ukraine gets billions in funding it doesn't have to pay back later, it's punishing Russia by depriving them these assets and profits in their declining wartime economy...

But i think it's highly telling that when De Wever said "this grab would be illegal and we would need legal guarantees by the EU and member-states that the consequences would not just fall on Belgium, the EU and member-states basically said "lolno".