During your turn, Mounts and Vehicles you control have hexproof.
Whenever a Mount or Vehicle you control attacks, put a +1/+1 counter on it.
Deploy cheap, aggressive Mounts and Vehicles, then attack repeatedly to snowball +1/+1 counters while Miriam shields your crewed threats during your turn. You win through wide, evasive beatdowns backed by counter synergies and protection, turning otherwise-fragile artifact creatures into resilient, growing monsters.
Free +1/+1 counter on every Mount/Vehicle attack snowballs board state fast
Hexproof during your turn protects crewed threats from targeted removal and combat tricks
Low mana value (2) means easy, repeatable recasts after removal
GW gives access to strong ramp, go-wide tokens, and counter payoffs
Hexproof only applies on your turn, leaving Vehicles vulnerable on opponents' turns
Vehicles need crew, so a thin board can leave them as dead artifacts
Board wipes hit your token-based crew engine hard
Mount/Vehicle tribal support is still relatively shallow, limiting redundancy