Glad to see at least another perspective more or less echo my experiences/observations. You can't discount motivation, and bootcamps are filled with either those chomping to learn and explore, or those looking for the next goldrush. Adding to the challenge of differentiating is sometimes they are the same person.

Aren't most successful engineers already very smart when they start out? Being very smart seems to be a prerequisite for all successful engineers.

I mean I think I'm sorta smart but nah I have a 0 to bootcamp success story and I studied languages at uni and didn't even pass A-level maths in high school. I did a 3 month bootcamp. I was determined to end it with a job so I studied 12 hours a day 6 days a week. By the end I couldn't walk down the road without being out of breath but I had a job. My first year of employment was terrible. I was bad at everything and my employer had agreed to take bootcampers without any preperation of how to deal with that so just kept keeping me away from tickets, stunting my growth. After I wasn't renewed I spent a further 2 months doing intense studying and portfolio building and applied for my current job. They've supported me a bit and now 8 months in I'm a pretty competent junior I'd say. I feel like this is the level I should've been at at my first job but as long as you're willing to work at shitty companies for a bit you can just go from bootcamp to employed immediately and then work up to being good from there.

Edit: Whether I'm really worth the investment to these companies is another thing. I tend to think I'm not because I do sorta suck. But in terms of whether it's possible to go that path, be constantly employed and improve in time, yes it definitely is possible.