Of all the pirates in the area they chose to shut down the Wave? I can think of at least 10 pirates that should have gotten a visit instead of this guy in Boxford.
Probably the FCC got a complaint. The FCC's Enforcement Bureau, for better or worse, is mostly a REACTIVE agency instead of a PROACTIVE one. They need to receive a complaint from a party with standing before they'll act.
Being in Boxford, I would guess that there was a complaint from a listener to WBMT (2nd adjacent interference, when WBMT is on the air) or maybe WMBR (1st adjacent). Or possibly WBZ-FM (which would receive 10.6MHz I.F. interference, albeit in a pretty small radius...just takes one offended listener, though!)
I remember there was a pirate on 90.5 in the Dorchester area not far from the Boston Globe. That was a dumb move...I hear there were several complaints from Globe staffers wanting to listen to WBUR, and I'm sure a complaint was filed by WBUR itself, too. Said pirate barely lasted two weeks before a visit. Meanwhile, all the pirates in the expanded AM band (1610-1700 kHz) aren't interfering with anyone in Boston as long as they avoid 1650 too close to Logan...so there's no complaints from anyone with standing, and the pirates continue broadcasting for years.