There wasn’t much tension between chabad and the rest of the world until the last lubavitcher rebbe took over. The chofetz chaim did say that the only chasidim who the gaon would still oppose are chabad and breslov, but in terms of relations…there was very little hardcore hisnagdus after the kotzker rebbe and the yid hakadosh. It’s not surprising at all that the very litvishe Ohr somayach got along well with the rogotchover. It would be surprising if there was at that point tension.
The rogotchover found remozim to everything in torah, and was similar to the gra in connecting everything; the ohr somayach happens to do something similar in meshech chochma