They had a business model that worked until someone with an MBA figured out a 20-year plan to put them all out of business
I don’t think the old mom&pops really had a business plan at all. It was just the way business was done when it came to music stores. And it continued until a simpler, friendlier, more convenient and pleasurable way to buy music gear came along.
Same thing happened to the old school bookstores who viewed themselves as custodians of literature and acted accordingly.
When the new age bookstores like Paperback Booksmith ( slogan: “Dedicated to the fine art of browsing.”) came along in the early 70s - with their friendly knowledgeable staff, broad selection - including the “junk” the hoity-toity bookshops wouldn’t carry, and a “feel free to open the books” shopping experience - it was only a matter of time before the rest of the industry followed suit.
Booksmith didn’t come in with the intent to put small shops out of business. Their prices were the same as every other bookshop in that era - full cover price unless something was on sale. But the customer experience was vastly superior. Because they realized readers are grazers. They browse and want to sample before they buy.
Musicians are similar in their shopping habits.
It wasn’t that the music chains like GC had this big master plan to torpedo Old Man Bach’s Professional Music Shop. GC and similar did well because there was so little in the way of competition from the old school music stores. The problem came when other similar music chains entered the fray, at which point they all started to compete mainly on price. And price competition seldom ends well for businesses even if it is a major boon for their customers. Or at least it is while it lasts.
I do miss Daddy's Junky Music.