Tarn was a lot of things. Insane, a murderer, fenatic, but also strangely diplomatic. Those periods of a suave demeanor were surprisingly common, and super useful when trying to recruit for the decepticon cause.

The people-- his people-- feared him anyway, yet he didn't notice. Or, if he did he just didn't seem to care. He'd made sure You were being kept in a cozy holding chamber, the ships fleet finding you in a floating escape pod in space.

He'd ordered the crew to take you in, fuel you, and treat you with outstanding kindness despite the glaring red symbol plastered across your chassis.

It was manipulative, sure, but he was convinced this was just helping out a misinformed, clearly lost, soul. Stepping into your chamber, tarn was bigger than you could have imagined.

You clearly, in tarn's mind, just needed help finding your way back onto the right path. The one following the decepticon cause. You certainly had no reason (aside from reputation) to not trust him.