Why must I create my VueJS application before using ChartJS?

I have this very simple page, that works properly:

<!DOCTYPE html>
<html lang="en">

<head>
    <script src="https://unpkg.com/vue@next"></script>
    <script src="https://cdn.jsdelivr.net/npm/[email protected]/dist/chart.js"></script>
</head>

<body>
    <main id="vue-app">
        <p>{{ name }}</p>
        <canvas id="chart-flow-rate"></canvas>
    </main>
</body>

<script>    
    // Start VueJS
    const Application = {
        data() {
            return {
                name: "My Chart"
            };
        }
    }
    vm = Vue.createApp(Application).mount('#vue-app');

    // Use ChartJS
    const myChart = new Chart('chart-flow-rate', {
        type: 'bar',
        data: {
            labels: ['4', '2'],
            datasets: [{
                data: [4, 2],
            }]
        }
    });
</script>

However, if I invert the blocs of JS to use ChartJS first and then to create the VueJS application, the page no longer works: the chart is not shown.

Why?

I have noticed that I can change my HTML’s body a little in order to be able to use ChartJS before VueJS:

<body>
    <main>
        <p id="vue-app">{{ name }}</p>
        <canvas id="chart-flow-rate"></canvas>
    </main>
</body>

Again: why?

Thanks a lot! 🙂