I suspect that that period of lobsters being plentiful happened as the cod fishery started to reduce the cod population, and what happened to lobsters is what would happen to any prey species when a primary predator is removed.

The last time I was in Vinalhaven ME, I ran across a monograph "The Lobster and its history" in which the author tethered legal-size lobsters to a tile, then placed them in a cod-underfished area (bottom conducive to snagging nets and so avoided. Nets are stupid-expensive). The tether and tile was to keep the lobster from hiding in a crevice.

Average time before the lobster was eaten by a cod: five minutes (or maybe two; it's been a few years)

What it seemed to me was going on was: reduce cod, lobster population booms. Timing's about right.

Now they have another predator: us.

FWIW, I've seen lobsters in the 25-30lb range. I think the only danger they face is divers as they're too big to fit through the net cone of a trap. We have a minimum size below which it's not legal to take, but there isn't a maximum size, which IMO is unfortunate.