What makes you think Bush was duped?
I don't know if Bush was duped or not, I said that hopefully he wasn't.
That's the sort-of-accepted story of Souter; that Warren Rudman advocated on his behalf to John Sununu, who then did the same to President Bush the Elder. Sununu famously said that Souter was a sure thing, or home-run for conservatives. So Bush made the worst mistake of his Presidency and listened to Sununu, when good judges like Emilio Garza were available.
Rudman apparently brags about this deception in a book he wrote.
Of course it could be that Bush knew Souter was a liberal, and that he wasn't deceived at all as he secretly opposed giving the Court a conservative majority (which it eventually and finally would have had for a brief window of time until Byron White retired a couple of years later). I believe Bush was still defending his pick yrs after he left office, but that could just be the natural instinct of not wanting to admit a mistake.