It's actually sort of the opposite here. Telecom's let cable companies beat them to the broadband market. So cable internet companies are the market leaders. And telecoms are ceding the market to them and just taking whatever they can get without investing too much.
Verizon Fios is a good example, they built it to compete with cable, but they still can't get more marketshare (in overlapping markets). It's barely profitable.
Telecoms don't think it's worth investing to challenge the cable monopoly.
I think this speaks more to interconnection, like water and power and sewer, and even human (car, sidewalk, etc) transport, being natural monopoly networks for the "last mile".
Competition would still be possible on top of this network, just like you can have different delivery companies.
If consolidation had anything to do with it, wouldn't you expect exactly the opposite result? Companies to see higher margins in the monopoly wired market instead of the wireless market where they have more competition?
Cable companies and telecoms aren't consolidated. The problem is telecoms don't want to spend oodles of money only to make very little profit because the cable companies are already entrenched.
Verizon Fios is a good example, they built it to compete with cable, but they still can't get more marketshare (in overlapping markets). It's barely profitable.
Telecoms don't think it's worth investing to challenge the cable monopoly.