Just because the heart rate is elevated in both cases, that doesn't mean the context is the same. It's not the same cause, it's not the same result.

Exercise raising the heart rate is a consequence, that (the increased heart rate) is not the singular magic thing improving your health. With exercise there's a positive, body-comprehensive event going on.

Exercise strengthens the heart.

Cocaine (for example) damages the heart. It doesn't just elevate the heart rate, it does some vicious things to the heart, causing damage:

https://www.webmd.com/connect-to-care/addiction-treatment-re...