Blazor computes the DOM deltas in webassembly/.NET code in the browser and then sends those deltas to the translation layer which then performs the changes to the DOM. This process would get a considerable performance boost if webassembly were allowed to access the DOM directly.
Silverlight required a plug-in. That's a barrier to adoption that they never overcame. When plugins were outlawed it was impossible to continue Silverlight. Microsoft had seen the writing on the wall and had effectively abandoned Silverligt as a strategic product long before that. Blazor Webassembly is not in the same situation. Webassembly is not going to be pulled. Webassembly is objectively better than Javascript for the task of running code in the browser, so my prediction is that Javascript will be deprecated before Webassembly.
Silverlight required a plug-in. That's a barrier to adoption that they never overcame. When plugins were outlawed it was impossible to continue Silverlight. Microsoft had seen the writing on the wall and had effectively abandoned Silverligt as a strategic product long before that. Blazor Webassembly is not in the same situation. Webassembly is not going to be pulled. Webassembly is objectively better than Javascript for the task of running code in the browser, so my prediction is that Javascript will be deprecated before Webassembly.