I cannot reply with certainty, this is a mix of facts with assumptions but I hope it helps out.

During the late 90's Ecuador was dealing with a lot of economic issues, all this resulted in a financial crisis that hit as the new century started. Many banks went to bankruptcy and thousands of people lost their savings, their jobs, houses, etc. Just to give you an idea, at that time Ecuador's currency was the Sucre. In one week the currency lost 67% of its face value, after a couple of months the government fixed an exchange rate of 1 USD = 25000 Sucres. So you can imagine that getting a job was close to impossible.

Neighboring countries were not doing any better, Ecuador had a war with Peru so relations were not the best. And Colombia was not any better. Since people were desperate to look for work to support their families a massive migration started. If I'm not mistaken at that time Ecuadorians did not need an EU visa to travel to Europe, and Spain being a Spanish speaking country became the perfect place to look for work. There was a big migration to Italy as well given that as a latin language it was easier to pick up than other European languages. Being able to earn their salaries in Euros, and at that time having a cheaper dollar meant that families who went to Spain, Italy, etc..., could sent money back to their families. The resources send from Ecuadorians living in Europe back to their families were so significant that had the power to shape Ecuador's economy.

Now, the former president of Ecuador, Correa, began a project to promote the returning of immigrants back to Ecuador. It was considered to be successful, but of course many people already started new families so is most likely that the amount of Ecuadorian that remained is big.

Once again, this are not precise facts! Is a mix of opinion, reading, conversations, etc... but I hope it gives you an idea.