As to why not set and forget a WSM.
First, what fuel did you use? Lump can burn down pretty fast when you get up to 275. Second, ash build up can reduce the airflow enough to cause a problem, even with lump. It gets worse with Kingsford blue briquettes.
Hope things work out for you. Very good advise to wrap and crank up the heat.
Jim - Another transplanted Texan
Former KCBS CBJ
Large and Medium Big Green Eggs , Black 18.5" WSM, Blue Weber Performer - Stainless, Green Weber OTG Kettle , Brinkmann SnP Pro, and a Stainless UDS. One retired Portable Kitchen grill.
Red Thermapen, Maverick ET-732, EdgePro Apex Sharpener.
Avatar is the original 1951 Weber Kettle