Why is there a post-pandemic litter epidemic, and what can we do about it?

Anecdotally, looking around the beach and parks in our own area, we see a lot more garbage strewn around since the gradual opening up of society as the COVID-19 pandemic begins to recede (a bit).
To us locals, this is annoying, frustrating and all but inexplicable. Who are these people who are littering, and why are the coming to our neighbourhood and messing it up? Of course, I should have known that the good old BBC has already looked into this phenomenon, and approached the appropriate experts. Britain too has seen an upsurge in littering since the lockdown has been relaxed, particularly in its parks and beauty spots. So, what gives?
It has long been known that littering depends on "social proof", i.e. copying the behaviour of others. So, if a place is already covered in garbage, people are more likely to think it doesn't matter, and if they see someone dropping litter they are more likely to do it themselves. While this seems to be asinine and inexcusable to me - I don't do that, why do other people? - it does seem to be a psychological fact among the general population. It has also been shown that littering is more common among young people, who typically feel a weaker bond to their community. Those same young people are also apparently establishing their worth among their friends and peers by openly and deliberately flouting the rules (What? Why would they do that? That makes no sense. They could just as well establish their worth by setting a good example.)
Anyway, be that as it may, the pandemic has also had a direct affect on the littering situation. Like so many other things, garbage collection has been affected, and bins may remain overfull for longer. Restaurants and pubs remain largely closed, so people are heading out to beaches and parks to socialize instead (certainly, our beach has bever been so busy), so that there is a larger critical mass of humanity for the social proof and peer pressure to work on. In the same way, there is more take-out food being consumed, with a concomitant increase in the amount of disposable packaging and therefore garbage available to litter with. Plastic and over-packaging are, as usual, the main offenders. The psychological stress of lockdown itself may lead people to adopt more risky, even anti-social, behaviour (that might also explain the spike in public alcohol consumption among younger people, technically illegal here in Toronto, and their propensity to hang out in large un-distanced groups). And finally, some littering is very clearly pandemic-related: plastic gloves, masks, etc.
So, yes, there are some very specific reasons for what we are seeing. But that doesn't make it inevitable. I don't litter. I never have (at least in my adult life, since I developed a social and environmental conscience). So, others too can learn to think before they do things, take home their left-overs and packaging, no?
Apparently, it's not that easy. There have been a few prominent success stories (Taiwan, for example, by, among other things REDUCING the number of garbage bins). But all sorts of touted solutions - watching eyes painted on walls, fines, verbal appeals, information blitzes, novelty garbage bins, etc - have often met with limited success. Good old social disapproval, particularly from within a peer group, is one of the most effective, but that requires thinking young people willing to transcend their peer pressure. I rarely bother to take litterers to task when I see them, and maybe I should, although I know the reaction I will get nine times out of ten. Particularly effective, apparently, is when people see others picking up trash (especially THEIR trash) from the ground and disposing of it responsibly. I do sometimes do that, but I could do it more often, and perhaps more blatantly.
It's all about changing behaviours and norms. So, let's see what we can do about that.