There are many possible reasons
Perhaps Dish spent all this money to prevent Blockbuster from falling into the hands of a competitor who would have a use for it.
What is not known to me is whethjer they are actually buying shares and inheriting all the debts, or whether this is a debtor in possession deal where Dish lends blockbuster 320 million to bail it out, and then Blockbuster issues 320 million worth of new shares to convert debt into equity.
In the second deal, current shareholders get no money and see their equity reduced to a very very tiny percentage of the re capitalised company. In some cases (such as GM) they don't just issue new shares that dilute the old ones to next to nothing, but fully recapitalise a new company from scratch, which voids the old shares completely.
Having all those retail outlets will benefit Dish since it will be able to sell its satellite receivers and subscriptions at all blockbuster stores.