Did Guyuk forcefully take over and want your submission or had they been acting rather peaceful by responding to your letter instead of taking action first?
The Mongols spread diseases and plagues during warfare; impacted trade routes because it was harder during an epidemic where diseases spread easily and people were wary of buying from travelers because of this
“Destruction of Qanat Irrigation System” Destroyed something of important value needed to feed people and could have resulted in famine. Bad for trade.
Had organized government, laws, and punishments in place- Structured politics and gov. Law and Order make for safer travel and trading because of scams and theft.
“Built beautiful capitals” Public projects showing traits of civilization and it was for the people. Big cities encouraged trade and positively impacted exchange networks.