Basic React Route with dynamic ID not rendering component - reactjs

Question

I'm trying to figure out why the component SubPage is not rendering whenever the route path of /sub/:_id is visited (e.g. /sub/5f1c54257ceb10816a13d999). This is the first time I've worked with react routes. The :_id part should presumably accept query parameters from the URL dynamically so I cannot see why this is not working.
I can get the /subs page to fetch the API and render each sub on the page but just not each individual sub page.
The route is as follows near the bottom of App.js: <Route path={"/sub/:_id"} component={SubPage} />
Thanks for any help here. I've made a stackblitz for convenience, or you can see the relevant code below:
And subPage.js:
import React from 'react'
export class SubPage extends React.Component {
render() {
return (
<div className="sub-details-individual">
<h1 class="std-intro">Viewing a Single Subscriber</h1>
<div className="sub-specs">
<div className="sub-specs-inner">
id: {this.props.params._id}
</div>
</div>
</div>
)
}
}
And App.js:
import React, {Component} from "react";
import {navLinks} from "./components/nav-links";
import Root from "./components/Root";
import {
BrowserRouter as Router,
Switch,
Route
} from "react-router-dom";
import {SubPage} from "./components/subPage";
import ShowSubs from "./components/show-subs";
export default class App extends Component {
constructor() {
super();
this.state = {
navLinks: navLinks,
intro: "hello world",
url: "someurl"
}
}
updateURL = (newUrl) => {
this.setState({
url: newUrl
})
}
render() {
return (
<Router>
<Root navLinks={this.state.navLinks} intro={this.state.intro}></Root>
<Switch>
<Route path="/subs">
<p>subs page</p>
{/*this.updateURL('/subs') fails presumably because it causes the rerender infinitely - but how to solve?*/}
<ShowSubs />
</Route>
<Route path="/">
<p>homepage</p>
</Route>
<Route path={"/sub/:_id"} component={SubPage} />
</Switch>
<p>the url: {this.state.url}</p>
</Router>
);
}
}

Answer 1

Two things:
this.props.params._id will crash since you are missing match before params
this.props.match.params._id
few exact props are missing, especially in the subs path:
<Route exact path="/subs">
Note: the exact prop will be useful in the / route as well.