Wifi Tx rate in airport and speedtest cli upload/download speeds are drastically different
Tx rate is the speed of connection between your computer and the WiFi; this is not the same as the speed of your network connection provided by your ISP. So you might have a high speed in your local network, but accessing the internet has lower speed limited by your internet plan (which is what speedtest-cli tests for as it establishes a connection with a server somewhere else).
If you want to test LAN speed, use iperf on local devices.