To the editor: What lies behind the events that have unfolded at the Berkshire Museum over the past five months, triggered by the surprise hijacking of its treasured art collection? Overlooked in this debacle are the crucially flawed internal functions of the museum itself. I say this as a 20-year trustee of a similar regional institution, the Hudson River Museum in Yonkers, N.Y., a community with strong social and economic parallels to Pittsfield.