It's probably safe to claim that part of it (and what likely killed Flickr) is that the original owners are usually more able to make coherent product features and explorations. They built something in the field because they knew something about the field.
Once they're bought up by some other company, in particular any conglomerate, it gets worked on by a bunch of people who are experts at building products in general, not experts in that product's field. So they naturally try stuff that is less of a fit for the field it was originally targeted at... and potentially a better fit for "can make any money at all", I'm not trying to claim the new owners are all idiots. Just that the driving interests and expertise have shifted from what originally made it compelling, and that'll nearly always become less coherent as a product. At least until they have fully rebuilt it in their image.
And then purchasers in the same field can sometimes escape this "now built by generalists" trap. Sometimes.
You raise a good point but you are too generous. The buyer tends to be mercenary. I think generic "professional" management only ends well in mature products and companies, where the main task is to increase efficiency. I don't expect the buyer to innovate the product.
Conglomerates are IMO almost always mercenary and damaging, yeah.
They're far from the only company purchases happening though, e.g. many small companies that grow too quickly sell to something larger to simply have the manpower and money to handle the new scale, and sometimes that ends up better for everyone. You just don't usually hear about these because they quietly work, and they don't involve globally-recognized names.
Once they're bought up by some other company, in particular any conglomerate, it gets worked on by a bunch of people who are experts at building products in general, not experts in that product's field. So they naturally try stuff that is less of a fit for the field it was originally targeted at... and potentially a better fit for "can make any money at all", I'm not trying to claim the new owners are all idiots. Just that the driving interests and expertise have shifted from what originally made it compelling, and that'll nearly always become less coherent as a product. At least until they have fully rebuilt it in their image.
And then purchasers in the same field can sometimes escape this "now built by generalists" trap. Sometimes.