I added the following scripts before syncfusion scripts to _Host.cshtml
<script asp-fallback-test="window.Promise"
asp-fallback-src="https://unpkg.com/promise-polyfill@6.0.2">
</script>
<script asp-fallback-test="window.fetch"
asp-fallback-src="https://unpkg.com/whatwg-fetch@2.0.2">
</script>
but syncfusion controls still do not render in IE11