Element style has no effect

introduced in this way in the entry file

import ElementUI from "element-ui"
import "element-ui/lib/theme-chalk/index.css"

but the effect in the component is like this. why?

<template>
   <div class="txt">
    <el-button type="primary"></el-button>
    <el-button type="text"></el-button>
   </div>
</template>

<script>
export default {
}
</script>

<style scoped>
*{margin:0 ;padding:0}
html{-webkit-text-size-adjust:none;}
.txt{width: 100%;min-height: 1200px;position: relative;}
</style>
Sep.02,2021

guess Vue.use (ElementUI) did not write

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