A common thought when people first embark on an exercise program is that they’re going to lose weight and get really muscley. However the truth is it’s extremely difficult to do both of these simultaneously. Even professional bodybuilders focus on each goal separately.
You may of course notice people who were once overweight, looking stronger and leaner. However the most likely scenario is that they simply lost fat, so their muscle became more visually prominent. They may have seen minor improvements in strength if they were absolute beginners (these are often called beginner’s gains), but unless they focus on one area specifically they will not have significant results in either.