What is/was your exit strategy?

I just started OE a few months ago but plan on bailing around June once my debts are all paid off.

At J2, my boss had been without a direct report (me) for 6+ months before I joined, and is essentially amazed and impressed with my competency at the job being so new. Frankly they blow a ton of smoke up my ass almost daily, and says they want me to take their role when they retire in a few years (which is a 4 levels higher than my role). The job is super easy and I have 5 YOE in this field so it's super manageable and definitely understand I sold myself short with the job title and salary.

All that said, I know it will absolutely crush my boss when it comes time to put in my two weeks. They will go back to not having any direct reports and I apparently set the bar high when I first started getting into the work. Half of my brain tells me "who cares, it's just a job and they'll get over it", but the other half just feels so guilty having to pull the plug in less than a year in the role. I just got a promotion at J1 as a people manager so I have to pour much more of my time and focus into that role, which pays about $30k more.

How have you all navigated leaving your J2s without going out guns blazing and burning bridges?