Can Somebody Tell Me...

Why the Nazis attempted Operation Rheinübung in May 1941--why they sent the Bismarck and the Prinz Eugen on a commerce-raiding mission when the two ships might have been very nice to have for shore bombardment in the Baltic in the Russian campaign that was shortly to commence?

Why, given that the Nazis had decided on a large-scale surface raid, they did not use all of their ships--Bismarck, Tirpitz, Scharnhorst, Gneisenau, Prinz Eugen--but only two of them?

Why, once the Bismarck had been hit by the Prince of Wales and was leaking oil and thus had restricted range and speed, the Nazis decided to head the Bismarck for Brest in the teeth of the British fleet rather than withdraw back through the Denmark Strait and then back to Bergen?