So I'd never looked up the east thing before. Here's some things I found as "why".
"For as the lightning comes from the east and shines as far as the west, so will be the coming of the Son of Man" (Matthew 24:27)
"Ye men of Galilee, why stand ye gazing up into heaven? This same Jesus, which is taken up from you into heaven, shall so come in like manner as ye have seen him go into heaven." (Acts 1:11)
"And the glory of the Lord came into the house, by the way of the gate looking eastward:" (Eze 43:4)
"And if the prince should prepare as a thanksgiving a whole-burnt-peace-offering to the Lord, and should open for himself the gate looking eastward, and offer his whole-burnt-offering, and his peace-offerings, as he does on the sabbath-day; then shall he go out, and shall shut the doors after he has gone out." (Eze 46:12)
Seems like east-facing worship is a maintained inheritance frontman Israel.