Toddlers take their clothes off for several different reasons.
Some reasons that toddlers take their clothes off is they are uncomfortable in their clothes, they found out how to take their clothes off and love doing it or they love getting a reaction from you.
Then sometimes the toddler also takes their diaper off because they like the attention they are getting or they are uncomfortable wearing the diaper and hate the feeling of the diaper especially when it's wet or pooped in.
The same goes for clothes as in the like the attention they get from you.
If they are taking their clothes off you need to tell them sternly that they shouldn't do that and there are only certain times to take their clothes off such as when taking a bath or changing their clothes.
If they are in diapers tell them they must either wear the diaper or go to the toilet and if the toddler is still removing their diaper then try putting them in some Pajamas that zip up the back and put duct tape or packing tape around their diaper.