Details matter in nuclear diplomacy. The JCPOA was 120+ pages with technical details and 24/7 international monitoring. We haven't heard about such monitoring in this deal. The durability depends on enforceability and monitoring. This MOU might be a page and a half, punting hard issues to 30-60 day talks, which could unravel.
Iran believes it has the upper hand and will not end the war without significant compensation (frozen funds, sanctions relief). The US will try to withhold benefits until Iran takes agreed steps, but Iran will use the deal to rebuild its economy.