Why was my meat hotter than the oven?

Pressure inside the meat.

The thermostats on many ovens are notoriously inaccurate. My stove lets you adjust what the temp reads, if you find it’s consistently too hot or too cold, and it was off by about 15F. In order to be certain of how hot the food is, you have to put the thermometer in it while it’s cooking.

The meat – over time cooks and becomes hoter than the temp of the oven -

as the meat absorbs the heat.

The heat is conducted through the meat.

Convection. When meat is cooked by hot air passing around it, it cooks by convection. Cooking burgers in your oven is convection.
As the meat begins to heat, it undergoes physical and chemical changes. At about 120F, some of the fluids begin to get milky. As the meat gets approaches 140F, cell walls begin to break open and release liquids. This is what makes meat juicy. Raw meat isn’t very juicy because the cell walls are all intact. After the fibers break down the juices release more easily as you chew. That’s why a rare steak is juicier than raw steak.
At about 140F red meat begins to turn pink as the myoglobin begins to change. As the temperature rises and the myoglobin changes, the juices go from pink to clear, and the meat turns tan.
Also at about 140F, the heat causes the sheaths around the muscle cells to shrink rapidly and squeeze out moisture much like wringing out a wet wash cloth. It can happen suddenly, and the meat will rapidly shrink, stiffen, and become chewier. Juices will bead and pool on the surface. That’s why medium rare steak cooked to about 120F is much juicier than well-done steak cooked to 155F. This drying process even happens when meat is boiled. You would think that boiling meat would keep it moist, but boiled meat can get as dry as cardboard. Poaching or braising meat by submerging it in liquid below 212F, the boiling point, will not drive off the moisture as rapidly.
As the hot air circulates in an oven, the moisture on the surface runs off and evaporates. The lower the oven temp, the less evaporation, and the juicier the meat. Evaporation is not a problem with a big roast like a prime rib roast or a pork butt. If the exterior is a bit dry and crusty on a prime rib, pork butt, or brisket, no sweat. The interior is so far away that the moisture cannot escape.
Further cooking transforms more of the compounds in the meat. Some of them begin to escape as enticing aromas. This is no great loss. We smell powerful scents even if some aromatic compounds are as low as a few parts per billion.
The melting of collagen really starts to accelerate as the meat hits 160F and it continues rapidly on up to 180F. By now lean meat like steak or pork loin is well done and beginning to dry out. On collagen and fat laden cuts such as ribs, pork shoulder, or brisket, although the muscle fibers are drying and toughening, the collagen that held them together as bundles begins to turn to liquefy; the meat gets easier to chew and the gelatinous collagens makes the texture more pleasing.
Meanwhile the fat is softening, rendering, spreading through the meat to lubricate it, and dripping out. As it softens, fat absorbs the aromas and flavors from spices in the rub, marinade, brine, and smoke. If the meat gets too hot, all the fat will render out and rob the meat of much of its flavor and texture.
As the surface of meat heats above the 212F boiling point, it starts to brown, a process called the Maillard reaction, and it develops a richness and depth of flavor, not to mention crunchy texture.