Parashat Toldot: What's Going On Here?

What's going on here? מַה זֶה?

Why did Yitzhak give the בְּרָכָה (berakhah, blessing) to Yaakov?

When Yaakov dresses up as Esav in order to receive the berakhah, Yitzhak notices that something is strange.
וַיִּגַּ֧שׁ יַעֲקֹ֛ב אֶל־יִצְחָ֥ק אָבִ֖יו וַיְמֻשֵּׁ֑הוּ וַיֹּ֗אמֶר הַקֹּל֙ ק֣וֹל יַעֲקֹ֔ב וְהַיָּדַ֖יִם יְדֵ֥י עֵשָֽׂו׃
Yaakov approached Yitzhak, his father, and he [Yitzhak] felt him. He said: “The voice is the voice of Yaakov, but the hands are the hands of Esav.”
If Yitzhak was able to correctly identify Yaakov’s voice, then why did he still give him the berakhah?
Rashbam (12th century, France) explains that, since Yaakov and Esav were twins, their voices sounded very similar. For this reason, Yitzhak trusted his sense of touch more than his sense of hearing. The hairy hands that he felt made him believe that it was Esav, not Yaakov, who was in front of him.