There's been a recent update, so one or more of the mods may not be updated and it may be causing issues. There is also the chance that a mod is not playing well with others or native files that other mods have changed. Mods often conflict - just one of the many risks of using them which you've just learned. :)

READ THE MOD NOTES BEFORE INSTALLING. Most of the time the creator will have been made aware of conflicts with other files and will have hopefully advised what will stop their mod from working. It's also worth browsing the comments for the mods if you're using forums like Nexus or Thunder to search for mods.

There is no easy way of fixing the issue if you want to keep using the mods. (The easy way is, of course, just removing all the mods entirely and playing vanilla as others have suggested.)

Take them all out and add them one by one - test the game each time you add a new mod. If you don't want to test each one individually, just keep adding mods until the game crashes and then you have an indication of which one doesn't work or is conflicting with others. Time consuming but effective.

Next time don't just add a bunch of mods all at once. :)