In the electrophilic aromatic substitution (EAS) of pyrrole, why is the alpha position preferred over the beta position so much?
The following figure shows the resonance structures we can draw to describe the intermediates produced by electrophilic at the 2- ($\alpha$) or 3- ($\beta$) positions in pyrrole.
You can see that the intermediate produced by attack at the $\alpha$-position can be described by 3 resonance structures. Whereas attack at the $\beta$-position produces an intermediate that can be described by only 2 resonance structures.
Therefore, the intermediate formed by $\alpha$ attack is more stable and the activation energy leading to it will be reduced. Consequently, electrophilic attack at the $\alpha$ position in pyrrole is preferred.