If you suspect a crash to desktop due to low memory, you can tell for sure that this is the case by looking at Event Viewer > Windows Logs > System and scrolling down to the time and date of the last crash, your error should look similar to the screenshot attached.
It will also tell you how much virtual memory AOE2:DE was consuming at the time of crash. In my case with UHD enabled, the game was consuming 11.5GB virtual memory. This is on a system with 16GB RAM.
Not all crashes will be due to lack of memory, so looking at event viewer is useful to rule that out at least.