LCS is a reflection of what the currently strong champions and meta picks are. The reason you see champions picked in LCS nerfed are because the people in LCS use the strong champions. If there was no LCS or way to see top players play champions would still be nerfed because of how riot gathers information on champions from players that study the meta-changes from patches, so saying that LCS causes nerfs to champions is wrong, but not far from the truth since champions with an advantage in the meta are often picks LCS leading to an almost parallel correlation.
jk pls lcs stop play my champ
jk pls lcs stop play my champ