See Part I here: https://www.full30.com/video/6d247394d7def5ad3831275231a3fa70
The Sturmgewehr was the result of a German intermediate cartridge development program that began in the mid-1930s. It was sidelined for a period as the focus of German Ordnance shifted to full-power rifles in 8x57mm with telescopic sights, but as the German fighting in Russia became more desperate, many Ordnance officers realized that the greater firepower offered by the Sturmgewehr concept was one of the few options that might be able to allow depleted German units to effectively hold ground against Russian attacks.
To this end, the guns were issued primarily in the East, with whole companies being equipped in order to focus a maximum amount of firepower, rather than spreading the new rifles piecemeal across all units. Ultimately, of course, this was insufficient to prevent the growing Soviet advance - but for the individual German soldier, an MP-43/44/StG-44 would have been a much more comforting weapon than a Kar98k Mauser!
Sturmgewehr vs Kalashnikov: https://www.full30.com/video/5a5e03f95d231d7e1497e60c286cd595
MkB-42(H) with ZF41: https://www.full30.com/video/ecb06609072596f08e294235185ae9c9
StG-44 with Krummlauf: https://www.full30.com/video/0b8f8c4dc05119c30016e8974f6d5103
VG1-5 Last Ditch Nazi Rifle: https://www.full30.com/video/8cf42b984258db76bb96eb123aa52591