Well, the other example you used back on Saturday was the Netherlands. They, too, implemented a lockdown in early November after moving to a partial lockdown in mid-October. Their average daily cases trend is similar to Belgium and corresponds to the biggest reduction coming after a full lockdown.
It's correlation and not necessarily causation, but if people won't voluntarily comply with rational mitigation measures then what is a government to do? Just let COVID run amok and cause thousands of deaths? It's a serious question -- I'm not being flippant. The alternative to a lockdown is that people act sensibly and follow the voluntary mitigation measures laid out by public health authorities. The problem is that even if 75% of the populace are doing so, the anti-maskers and the "ain't nobody 'gon tell me what to do" crowd are choosing not to follow the voluntary mitigation measures and that's why governments are exasperatedly implementing new lockdowns.
I picked Belgium/Netherlands moreso because they were the first to see such large surges, and their pattern of peaking basically 1.5-2.5 months into the surge fits with just about everywhere else, regardless of the amount of restrictions. They perhaps aren't the best example of post-peak pattern because of the lockdowns.
As for your second paragraph (yes, there's some tin-foil hattiness in this, but bear with me), I think the reaction and how places handle this virus is still directly related to what now appears to have been blatant Chinese propaganda coming out of Wuhan in January/February. The people falling dead in the streets, convulsing in the streets, etc, and estimated IFRs of up around 5% or higher frightened the entire world for obvious reasons. It sounded like it was a more contagious SARS or MERS. I think a lot of the people and governments still treat this current virus that is circulating as if it is the same virus we saw videos of from Wuhan, when it clearly isn't.
If we had been warned of a virus that would be equal to or less deadly than the flu for young, healthy adults, but roughly 5x more deadly for the elderly than the flu, would the world have panicked as much as we did and treated this the same way? Obviously I know it is more contagious than the flu, but how many flu deaths a year would be attributed to it if we counted flu deaths the same way we do COVID deaths? I wish it was more than a hypothetical scenario, but unfortunately it isn't. I don't know what the actual number of COVID deaths are, but I'm quite skeptical with how we report COVID deaths, where basically anybody that dies within a certain window after having a positive test is considered a COVID death.
I was as pro-lockdown as it came when this first started, largely because I was scared of what I saw coming out of China. I started grabbing double of most grocery items by the first week of February so that by the time March came around I had a freezer full of food and a couple extra shelves stocked. I have done almost a full 180 on that position since the spring, especially on the large scale. Even if I was still in support of lockdowns, the biggest mistake the US made was treating everywhere equally and locking down areas that had very little virus. But I suppose that's another topic all together.
I think we should have (and should be) encouraging young people to live their lives as normally as they can, and try to develop ways to help keep seniors isolated (if they want to be). Increasing spread among young/healthy adults in the long run will protect the older less healthy adults. Restrictions tend to even out the spread among all age groups. A good example of this was Florida during their summer wave, where the positive cases were much more plentiful in the younger demographics. Back in the spring in the NE, most positive cases were in the older age groups, though testing for symptomatic people only likely skewed that a bit.
There's another angle to the story and that is the prospects of a good vaccine. I'm less against restrictions if it is a guarantee of a good vaccine on the near future. Obviously the current news is optimistic, but I'm still skeptical given the relatively small numbers of people in the trials and that this vaccine is still the first of its kind. If you have major side effects in say 0.25% (I'm pulling this number as an example, not the study) of people, but mass vaccinate people, you likely have caused more harm than good, at least for the younger generations.
I'm not good at putting coherent long winded posts together like you are (this is actually meant as a compliment, heh), so forgive me as I bounced from point to point somewhat erratically in this post.