I think with sky they entered the broadband market as a means to retain TV customers, so was never a primary focus for them.
However ironically they didnt do it the cheapest way possible from a capital cost of point of view, they brought an entire isp (easynet) to gain a national network, and were the only big player during the dark adsl max days to have unlimited usage unshaped traffic (largely uncongested as well). (not on sky access tho). Also they enabled g.inp on ADSL in their LLU exchanges, several years before openreach VDSL seen it. Also makes a mockery of the fact UK ECI VDSL doesnt have it.
In recent years tho I have an opinion they have been cutting back on expenses, probably to max the sale value to comcast. Football as a profit making machine I think the days are numbered, so sky are in limbo land in my view. I dont have much faith in comcast to invest either.
Talktalk is just as big a player as sky, and probably when you factor in that they wholesale their network then are probably a bigger player.
Vodafone I consider a bigger player because they are a large established mobile telco, that is a much much bigger and stabler foundation than EPL football rights, which are not a physical asset. Sky's assets is basically the easynet network and some LLU equipment. They even rent not own their satellites.
To put into perspective, BT once they decided to compete on TV were able to setup the operation very quickly in a year or two. Sky would never be able to duplicate what BT have in terms of assets in that time. The movie companies also are moving away from the type of deals that allow sky movies to work, the future is looking dodgy for sky and if I had shares I would be selling them up.