A single Tweet embed consists of two components: a <blockquote> HTML element and Twitter’s widgets JavaScript running in the same document context as the blockquote to enhance the markup.
If you are seeing an unstyled Tweet embed it’s likely Twitter’s widgets JavaScript was unable to load and act on the content.
https://platform.twitter.com/widgets.js
If Telerik AppBuilder includes a resource manager for JavaScript files you may need to load the JavaScript through that resource manager. If you are trying to load the widgets JavaScript from the HTTP scheme instead of HTTPS you may run into issues with Apple’s Transport Security; make sure you are using the HTTPS URL and try whitelisting the platform.twitter.com domain in your app’s Apple Transport Security settings to help debug your issue.