It's said that anxiety can develop heart diseases. in both the anxiety and exercise, heart beats go up but why can anxiety cause disease?

Not so sure: the interaction between stress, anxiety, and heart disease has never been entirely certain. I'm sure on some level anxiety and stress can cause deviations in healthy lifestyles, and perhaps in this way heart disease can be fueled or triggered.

Primarily associated: with chronic anger/hostility along with life changes, both bad (& less so) good ones. Anxiety/fear associations have not held up. Primary documented physiologic drivers are lipoproteins (not cholesterol), blood sugar >low normal, chronic resting systolic BPs >120, smoking & other less freq issues. Ds progresses over decades & ↑ed pulse pressure (exercise & anger) ↑es incidence of plaque ruptures.