Noone asks you to use Brython. People familiar with Python might prefer writing their frontend code in Python just because they are already familiar with it.
The following argument isn't necessary for folks who do want Python in frontend but still, not all of your points hold true, Python can handle multiple commands in a single line and it does have anonymous functions: lambda.
I would differentiate between marketing speak (designed to replace Javascript) and the practical implications of Brython (designed for folks who want to use Python in frontend)
If I were a JS developer who only wanted to write JS, but I needed to do a database query, should I look for a database that lets me write queries in JavaScript (or a language basically interchangeable with JS)? Or should I just learn SQL?
Sometimes as a programmer you need to learn new tools for new domains, and that's not necessarily a bad thing.
Too often I've seen companies stuck with an old framework just because their developers are used to it. That's how you get a microservice architecture in Java where each containers takes 300MB of space, and requires 1GB of memory.
I'm frankly amazed that the people who brought us node.js haven't also created a JS query language, furthering the spread of the triple-equals to new and greater heights.
The following argument isn't necessary for folks who do want Python in frontend but still, not all of your points hold true, Python can handle multiple commands in a single line and it does have anonymous functions: lambda.