Anyway I can avoid this in the future?

Hard to say without knowing what it died of. That's just pretty much what they look like when they die. Marginatas often die of overwatering, but it could have been the heat as well. Was it getting mushy at all before? Was it putting on new growth? Check the soil and the roots to see if they're rotted.

Does the pot have a drain hole in the bottom?

Looks to me like that marg died of terminal rot. It starts in the roots, and if you can catch it before it gets into the stem tissue, you can repot and the plant should be okay. Even just drying out the soil will usually be enough. But once it gets to the stems and makes them mushy, plant is a goner, even if the leaves are still green and standing up. But the leaves can wilt and fall almost over night, just like this one did. If you cut the stem, it will smell bad. In the future, make sure the soil is dry all the way to the bottom of the pot before you water again. And you do need drainage hole in the bottom of the pot.

That's what I was thinking about when I asked about the drain hole. Sometimes they don't come back, so I didn't say more.

thank you everyone! I noticed that the soil way somewhat dry. I feel like it could have been the dramatic change in temperature.. Normally Seattle does not get up to 93 degrees

A couple of things that might help you to understand what might have happened. Plants often don't show signs right away when something goes wrong; often, especially in plants like the marginata, you don't see a sign (except MAYBE a few yellow leaves) that the roots are rotting until the whole plant is basically dead. And feeling the soil on the surface doesn't really help - you have to check the soil moisture down near the bottom of the pot. That's where all the roots are. Even if the soil is all dry now, if it was wet for a month or so at an earlier time, the rot could get started. Once it gets started, it's almost impossible to stop.

However, I'm like about 99.99% sure the heat had nothing to do with it. Heat and humidity just aren't the factors that many people think. After all, the things are native to the tropics, and their adaptability is what has made them so significant as indoor plants. The only thing that can really kill them is wet roots.