The direct product
$$
e^{-\frac{1}{2}\vec{\alpha} \cdot \vec{\sigma}} \otimes \gamma_0
$$
means that the isospin Pauli 2x2 matrices are orthogonal to the Dirac 4x4 matrices.
To reinforce the point, you may rewrite the isospin Pauli matrices $\sigma_i$ as
$$
\sigma_i \equiv \sigma_i \otimes I_{4}
$$
and the Dirac matrices $\gamma_\mu$ as
$$
\gamma_\mu \equiv I_{2} \otimes \gamma_\mu
$$
Therefore the commutative relationship between the two sets of matrices is manifest.
To help you visualize $SU(2)$ doublet further, you can regard the doublet as (note that if we work in the chiral basis, the 3rd and 4th Dirac components of left-handed fermions are zero)
$$
\Psi_L \equiv \begin{pmatrix}
\psi_{\nu_l}\\
\psi_{e_l}
\end{pmatrix} \equiv \begin{pmatrix}
\psi_{\nu_l1}, \psi_{\nu_l2},\psi_{\nu_l3}, \psi_{\nu_l4}\\
\psi_{e_l1},\psi_{e_l2},\psi_{e_l3},\psi_{e_l4}
\end{pmatrix}
$$
with Pauli matrices multiplying from left of $\Psi_L$ (i.e. $\sigma\Psi_L$) and Dirac matrices multiplying from the top of $\Psi_L$ (i.e. $(\gamma\Psi_L^T)^T$). You may interpret the multiplication rules as Pauli matrices $\sigma_i$ mixing between columns of $\Psi_L$ and Dirac matrices $\gamma_\mu$ mixing between rows of $\Psi_L$.
Of course, in text books, $\Psi_L$ is typically manipulated via the tensor notation
$$
\Psi_{L\alpha\beta}
$$
with indices $\alpha$ and $\beta$ contracting with isospin and Dirac matrix indices, respectively. Then you can forget about the matrix related mumbo jumbo and peacefully spectate the forthcoming Tuesday speech and Wednesday finale.