There's no way to really explain that in lore - but also no reason too: just make the change, and pretend it always was. Players are willing to just go with a solid change like that for solid reasons - you ruin it once you try to explain it in-universe.
I had most of my fun playing ME1 trying to take ridiculous long shots on targets outside of the radar range. With some configurations of mods, which ME2 also slashed, this was really effective and kind of hilarious. Some of the physics damage mods on sniper rifles would blow enemies right into the air.
To anyone who thinks ME2 is better, I can only recommend this mighty analysis of the series: https://www.shamusyoung.com/twentysidedtale/?p=27792
Lots of parts, but it highlights all the problems of the second and third games really well.
Very different case, I'd say.