Thanks for the advice all

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Hey all so going to organize this into two parts. For context I’m a third year associate in a transactional practice. I lateraled from a V10, where I was a bankruptcy associate, to a V50 where I now do purely transactional work.
(1) just got my in house offer in this week - commercial/corporate counsel position at F100 tech (not FAANG). Comp is 220k, 15% bonus target, 20-40k in RSUs (negotiating) - so about 275-300k all in. Provided that the stuff in (2) tracks, this is a pretty great deal for a lawyer at my level right? I’m reading this as just about as strong of an in house offer that I could have hoped for, and think it merits hopping off of the Biglaw train a year or two early. Practically speaking I’ve only just now started to make the 250k third year salary so it won’t be a big practical change from my second year 225k. My firm also requires hours for bonus, which I won’t hit, so a bonus that I’ll actually earn most years seems nice. The environment seems nice at the company as well. F100 can sometimes just be Biglaw 2.0 but at the very least my read on everyone who would be working with me directly is they they are all very relaxed people.
(2) I’ve been at my new firm for less than a year. I took a risk switching practice areas and it did not pay off - really not a fan of the new practice area (multitude of reasons that are all fundamental to the practice). The in house role is much more generalist and I’m as confident that I can be that I’ll enjoy it more.
At my firm, I think I’m socially well regarded as far as attending events, having a good attitude, etc but I suspect I’m not overly well regarded professionally at my firm as I’ve only billed a 150+ month once and, through a combination of the firm being slow and my not marketing for work aggressively (hating the work, unable to mentally commit to a career in this practice group, likely to my own detriment), am not a profitable biller by any means. It’s been a tough process of interviewing for positions while also acting like I want to improve, get more work at my firm, etc.
Overall I’d like to leave without at least burning bridges outright. I’m unsure of whether certain partners will be quietly relieved that I found a way out or upset that I rolled in, took my signing bonus, and left without doing all that much work. Any advice on how to approach? I’m unsure of whether to take an “it’s not the firm it’s just that this job is great and I think it’s best for me” approach, or more of a “this is just a deal that didn’t work out” (with some explanations available in the unlikely event that this meeting lasts longer than 10 minutes).
Ultimately I understand that I don’t even merit a footnote at this firm, but it’s much better in my opinion to keep things amicable, so any advice on how to handle correctly is appreciated.