It certainly didn't take "an educated bettor" to put money on the likelihood Brady was coming back. The guy couldn't even give a straight answer for days and days last month when the story of his "retirement" initially leaked.
In fact, the line on him coming back was, 2 days after he announced on Feb 1, +750. To put that in perspective, the Bills are the only NFL team currently under +700 to win the SB. Brady unretiring was considered more a better bet than any team but the Bills winning the SB.