You are correct in that statement but all except Blackburn have their original "main" benefactor (and look at what is going on their at this time) and none of them have had more than one main benefactor - the same number that Pompey had before it went sour and I think you may have missed this. Of any of those other clubs you have listed were to lose their current benefactor and cannot replace like-for-like, that is when the pooh hits the fan, exactly what happened with Pompey.
I would guess that the majority of English clubs, have always, or most of the time, relied upon private money being put into the club by owners/directors. However, until the advent of the Premier League, those who invested in clubs were almost universally local business men, and more often than not could be correctly described as genuine fans of the club. In NCFC's case, you can think here of Arthur South, Geoffrey Watling, Robert Chase, and today Delia Smith and Alan Bowkett. Currently Wigan and Swansea are examples of clubs of which the same could be said, as, before his death, could Jack Walker's Blackburn. The difference today is that clubs are being taken over by people who have no roots locally and who by no stretch of anyone's imagination can be called true fans of the club. So the crucial question becomes: What are these people in it for? Unless you have the right answer to that question, there is no way of judging whether the club is going to be safe in their hands or not. The more sceptical of us obviously favour the relative safety of local ownership by true fans of the club. It can still go wrong if the local owners make poor decisions, die suddenly, go bankrupt or whatever. But at least the sort of question marks which hang over people like Abramovich, Al Fayed, the Glaziers, Lehrner, Ashley, Fernandes etc. don't arise. That said, it is wrong IMO to assume that every non-local non-club fan owner must be bad news. There can be answers to the question "Why are they in it?" which might allay doubts and fears about the long term commitment or local affiliation. To take Fulham's Al Fayad as an example, the cynical view is that his ownership of Fulham is part of his personal campaign to "authenticate" himself in this country and secure British citizenship, so far denied to him. To suddenly pull out and leave his "local" club in the lurch would be hugely damaging both to that objective and his "local" business interests (e.g. Harrods). So even if the cynical view of his motives is correct, his ownership is unlikely to seriously damage the club. Or take Southampton, they were rescued by a Swiss businessman, Marcus Liebherr who, as far as I know, had no previous connection or affiliation of any sort to the club. He was persuaded to invest by Cortese, on what grounds I don't know, fell in love with the club, became a genuine fan, and was adored by the supporters. So committed did he become in the short time he was involved (before his sudden and unexpected death), that he set things up in such a way that the club would continue to benefit from his involvement whatever happened. (This anyway is how I understand it; Saints fans will perhaps elaborate.) Cortese only played a part in rescuing the club, as I understand it, in a sense similar to the sense in which you might say DM has played his part in rescuing NCFC. IMO then, blanket condemnation of foreign ownership is unwarranted, likewise blanket approval. Each case needs to be examined carefully on its merits, with due diligence. Our board did so when Tony Fernandes became interested in our club, and politely said "No thanks!". His involvement with QPR (where the real wealthy backer is not Fernandes but Mittal) has started pretty ludicrously, but it is far too early to make a proper judgement. Manchester City seems to me to be in safe hands. On most of the others the jury is still out. Given time, even the owners of Blackburn may turn out to be more committed and sensible than currently appears.
