There are several factors that have prevented black players from becoming managers and discrimination is certainly one of them, though that is thankfully beginning to change.
Another reason is the influx of foreign managers from countries without a tradition of black players such as Spain, Italy, Germany, Argentina, uruguay, scandinavia and eastern europe.
One big influence is actually the high number of Scottish an Irish managers taking jobs in English football. These two countries have had a handful of black players between them and will never provide any black candidates.
Of the black managers that have worked in the EPL, Ruud Gullit (holland)did a decent job at chelsea but was rightfully sacked by newcastle, jean tigana (france) did ok at fulham but there could be no complaints about his departure, Terry connor who took over from boring macarthy at wolves wasn't up to the job and himself admits to being a better coach than manager, Paul Ince (england) should have been given more time at Blackburn but who hasn't that club stitched up? (he'll make it), Chris hughton is doing an excellent job at norwich as he did at birmingham.
Down the leagues their certainly should be more black mangers like Chris powell and i'm sure the numbers will steadily increase.
P.s don't listen to john barnes he was rightfully sacked by celtic as he didn't have a clue.
//flooded with black players// - unbelievable.