There are plenty of examples with one solution to a problem. 1+1=2, for example 😉 Of course you can have multiple solutions to many problems, but there is always an optimal solution. E.g. most people chose a chair instead of a dog to sit on. It's the same with money. Maximalist are simply people who have come to a similar realisation as those who chose to sit on chairs instead of dogs. It just takes longer to come to the realisation because money is a more complex issue. Most bitcoin maximalists also lost money on altcoins before becoming maximalists. It's part of the learning process.
Discussion
I could argue that 1+1 is a proof. Maths solutions are always proofs.
What we usually mean by a solution is a method or mechanism.
Many people prefer stools or beanbags. And when you describe people reaching the same conclusion. I would call that a consensus rather than a realisation.
On your last point we seem to have different premises.
I don't think filecoin or Nexo are good investments. But I do think they're interesting ideas.
Not every use of blockchain will make money, but that isn't the only reason to use a system.
Gold isn't only used as measure of value. It has even more valuable scientific uses.
Nano materials will get cheaper and cheaper but their utility is beyond monetary value.