Hello I can answer your question. From what I understand, the Imam have been instructed by Awqaf to lock the doors of the Masjid after the prayers are over. The reasons are below:-

1. The Masjid is a prayer for worship and the sole purpose of the Masjid is for prayers only. What has happened in the past was that most of the Truck Drivers, Laborer (Muslims & Non Muslims) have the Masjid as a place of rest, to sleep, to talk, to have lunch and kill time relaxing in the cool and quite environment of Masjid, oftening dirtying the place with dirt.

2. Also the wash room of the toilets for the faithful to perform wadhu is being used for Showers, laundry by these workers and so on. Even now in the souq area you will many non muslims using these toilets to answer the call of nature, but they don't ensure cleanliness.

I know its hard for these poor people as there are absolutely NO public Toilets in Doha City. But the Masjid is not to be used for this purpose !!

So i guess this the real reason. The Masjid was also used by many homeless people as well who are either absconding from their sponsors for any other reason as well.

That's all from me.

Good Luck and Have a Nice Weekend !