How does bad fuel damage the HMU multiple times but not affect the airline?
Mr Smith,
Bad fuel will damage EVERY HMU fitted to the aircraft until all the bad stuff is out of that particular system. In other words, if it's the left hand wing/tanks for example that uplifted bad fuel, the left hand engine/s depending on type will experience problems.
As for the damage to the airline, I can only assume it's to reputation, prestige and the bank balance.