Choice of the brand ambassador is driven by the customer segment that brand wants to target. For example, John Abraham endorsing a budget commuter might not be a good choice as John would appeal more to youngsters who want more power/looks in their ride. In that respect, I think AB is a good choice for brand ambassador as he gives the subconscious cues of maturity/versatility/reliability/trust to the brand Jupiter: appealing more to the middle class, mature customer segment TVS is targeting.

(My assumption is that TVS wants to target the middle class, mature customer segment for Jupiter. Please correct me if I am wrong here)