In my particular case, I did quit my job before I got my "real" Data Science position. I can't recall exact timelines, but I think I had already lined up the relationship with the startup.
The reason I did this is because there just wasn't enough hours in the day, and my job was taking ~10 hours a day with commuting...etc. It was a risk, but the idea was that I would be able to transition much more quickly if I worked full-time towards it. I also had the financial savings to support myself for 6-9 months and was willing to get a part time job if necessary. Once it became clear that my job's only purpose was to pay the bills in the context of my goals, and I had enough to pay the bills for the near future, it was clear that quitting was the easiest way to free up a lot of time.
This turned out to be the best decision of my career, but YMMV. I doubled my salary in less than 2 years. It's also nice to be part of an industry that isn't so cost-sensitive. I also have a skill set that's in much higher demand, so you can live almost anywhere and there's a ton of companies that want/need it. With semiconductors, you're much more limited.
It's true that you're giving up some expertise and will start in a less senior position in a different field than if you stayed in semi. Sticking around because you have experience is classic Sunk Cost Fallacy. Think 5 years down the line. If you leave now, you'll have 5 years experience in ML. You'll definitely be giving something up if you leave, but there's huge opportunity cost if you don't leave.
The reason I did this is because there just wasn't enough hours in the day, and my job was taking ~10 hours a day with commuting...etc. It was a risk, but the idea was that I would be able to transition much more quickly if I worked full-time towards it. I also had the financial savings to support myself for 6-9 months and was willing to get a part time job if necessary. Once it became clear that my job's only purpose was to pay the bills in the context of my goals, and I had enough to pay the bills for the near future, it was clear that quitting was the easiest way to free up a lot of time.
This turned out to be the best decision of my career, but YMMV. I doubled my salary in less than 2 years. It's also nice to be part of an industry that isn't so cost-sensitive. I also have a skill set that's in much higher demand, so you can live almost anywhere and there's a ton of companies that want/need it. With semiconductors, you're much more limited.
It's true that you're giving up some expertise and will start in a less senior position in a different field than if you stayed in semi. Sticking around because you have experience is classic Sunk Cost Fallacy. Think 5 years down the line. If you leave now, you'll have 5 years experience in ML. You'll definitely be giving something up if you leave, but there's huge opportunity cost if you don't leave.