原因・理由N1
〜と（が）相まって、〜も相まって
combined with... / together with... / coupled with...
Structure
N + と（が）相まって；N + も相まって
Explanation
N + と(が)相まって: two factors work together, producing a result.
Examples
努力と才能が相まって、彼は成功した。
Effort and talent combined, and he succeeded.
好景気も相まって、新店は連日満員だった。
With the economic boom as well, the new shop was packed every day.
Note
Multiple factors working together; common in news and formal writing.