Remember HTTP/2 - HTTP/3 Explained
One of the primary features of HTTP/2 is that it makes use of multiplexing, so that many logical streams are sent over the same physical TCP connection. This makes a lot of things better and faster. It makes congestion control work much better, it lets users use TCP much better and thus properly saturate the bandwidth, makes the TCP connections more long-lived - which is good so that they get up to full speed more frequently than before. Header compression makes it use less bandwidth.
With HTTP/2, browsers typically use one TCP connection to each host instead of the previous six. In fact, connection coalescing and “desharding” techniques used with HTTP/2 may actually even reduce the number of connections much more than so.
HTTP/2 fixed the HTTP head of line blocking problem, where clients had to wait for the first request in line to finish before the next one could go out.