For example, I used keep hiit, and it was reduced from 200 kg to 170 kg in three months. On the other hand, the period of muscle gain is recorded in years. A while ago, I mainly practiced chest, and my chest circumference only increased by 2 cm in 3 months.
People you see with obvious training marks often have a fitness history of 3-5 years or even longer, so it is really urgent to gain muscle.