> As for upper bounds, de Bruijn showed back in 1950 that {\Lambda \leq 1/2}. The only progress since then has been the work of Ki, Kim and Lee in 2009, who improved this slightly to {\Lambda < 1/2}. The primary proposed aim of this Polymath project is to obtain further explicit improvements to the upper bound of {\Lambda}. Of course, if we could lower the upper bound all the way to zero, this would solve the Riemann hypothesis, but I do not view this as a realistic outcome of this project
To your point, there was some excitement and progress in the beginning, but it remains an unusual approach to mathematics.
In experimental science, the number of coauthors of a paper has increased, but probably not the number of active coauthors.
Even business is born out of small startups, later expanded into larger teams.